Sparpreis tickets for 2 in Germany

Again, your Oldenburg-Osnabruck leg is fastest on a direct regional train entirely in the German state of Nord Rhine-Wesafalia, so you can just buy the laender ticket at the station for 26 euro out of the machine (extra 2 euro to buy from a human being). That covers both of you.

You might look at changing the order of your visits. Amsterdam to Osnabruck can be done as a direct IC train and there are 19 euro per person Sparpreis fares available. Use regional ticket for Osnabruck to Oldenburg per my last post. Oldenburg to Quedlinburg is just as fast using regional trains as IC trains, just one extra train change (some IC routes still require 2 changes) so you can use the Q.d.L ticket for 52 euro for 2.
Quedlinburg to Marburg and Marburg to Basel can be done with Sparpreis tickets if you want to save time and train changes.
With Sparpreis tickets, as time goes by, the price only goes up. If it is a popular route, it goes up fast. If not, it goes up more slowly, but on departure day, it will be full fare.

Unless the system has changed since 2012, you don't pay extra for online booking. You print out the tickets at home (the site says to use A4 paper, but 8.5 x 11 worked fine). On the train, you need the printout and the credit card you used to book the ticket. The conductor scans your printout, swipes your credit card, and you're set.

We got reservations for our prebooked routes (Berlin to Dresden and Dresden to Berlin) at the time we bought the tickets; they were optional on that route. However, we were very glad we got them, since these trains were crowded and we had luggage. The reservations cost €4 per person at that time (I believe I've read here that's gone up to €4.50). We saved a fortune by getting the Sparpreis. This train was €38 per person each way full fare, €19 for one person with Sparpreis fare, and €29 for two people with Sparpreis fare. So, on that one roundtrip we saved €94!

Possibly amusing side note: when you book a ticket for two, it's in the name of the person who booked the ticket, and just indicates that it's good for that person and one other (not named on the ticket). I had booked the ticket, and we had fun joking that my mother was my "plus one" on that ride.

For our other trip (Dresden to Goerlitz), reservations were not necessary or possible, and the Saxon ticket (like the Nordrhein-Westfalia ticket that's been recommended to you) covered the whole thing (easy to buy on day of travel from a machine).

"I understand from the DB website that reservations are required for Sparpreis tickets. "

Not sure where you read that on the DB website since reservations have not been required with SparPreis tickets for quite a few years, except for the rare ICE Sprinter, which requires seat reservations with any ticket. When I bought discount tickets, then called Dauer-Spezial, in 2008 reservations were optional.

But for longer trips, at 4,50€, a reservation makes sense. In 2012 I went from Bad Schandau, east of Dresden, to Freising with train changes Dresden and Hof. The Bad Schandau to Dresden leg was by reservable EC, the other legs were regional trains. Since the EC leg was only 28 min I didn't make a reservation. I figured if worse came to worse, I could stand for 28 min, but there were plenty of unreserved, unoccupied seats.

It should be noted that SparPreis tickets are not offered for all-regional connections. You can string multiple trains together to get to your destination, but at least one train must be a train of the Bahn (IC, ICE, or EC), and that train is the only train for which the ticket is valid. For the regional trains, you can take any other regional train on the same route from midnight of the first day of validity to 10 AM the following day.

German Rail reservations are for up to 2 trains in one direction. So, if you have, for example, an ICE/IC connection, for 4,50€ you get seat reservations on both trains.

I just purchased tickets today for Munich to Berlin on an ICE train. I did pay the additional price(4.50 euro per person) to reserve seats as I have been on some trains in Europe in the past where it was difficult to find a seat. Also, before I finalized the purchase, I was able to see the seats that were selected for us. I ended up changing our seats, but there was hardly any left to pick from. Apparently, that is because I purchased the Sparpreis tickets, which are limited. The tickets were a great deal less expensive than the price that RS has on his point to point map. Our travel date for that trip is Sept 14th, so it is not to early to book.

I don't think the reservation system of DB looks at what kind of ticket you have when assigning reservations, so reservations are just as available with Spar Preis tickets.

You can purchase reservations independent of you ticket. Many people in German have yearly Bahn cards, which covers travel on any train, and only have to get reservations, if they want them.

For completely domestic connections, you can purchase the tickets at one time, then purchase a reservation at another time. When you purchase the reservations, you don't have to tell them what kind of a ticket you have.

All of you have added so much to my understanding. I may have been confusing the German Rail Pass Promo with the Sparpreis tickets. So many little things I didn't know, like about the A4 paper. (We'll try our usual size; one more example of the US being out of sync with the rest of the world.) Thanks much.