We had the double snap-n-go when our girls were tiny. It's the frame that lets you snap 2 of the infant carseats into it. Definately got our money's worth & then some out of it! From day one (well, day 7, since they were in NICU for a week LOL) they tended to fall asleep in the car (still do if it's naptime LOL) so it was great to get somewhere & be able to just snap the carseat into the snap n go and let them keep sleeping. I also used it for walks in our neighborhood that first summer & loved that the babies were facing me & that I had the fully adjustable sun shades from the carseats so I could make sure the sun wasn't on them. And, just like in the car, they fell asleep pretty quickly/easily during walks in the stroller so I got lots of exercise that summer letting them sleep while i walked.
Once they outgrew the infant seats we had(have) the Peg Perego Aria but they never really "took" to it. They couldn't see me, which they didn't like when they were little. And while the Aria is narrower than a wheelchair, it IS still hard to get back into the racks in a dept store or something. And well, they just never were much of a fan of riding. I do think it was the best option when we got it, but we didn't really get our money out of it. I ended up just using an umbrella stroller & slinging the other one.
A couple months ago someone on the yahoo apmultiples board posted a link to the Marco Sky L http://www.2became4.com/ProductDetai...?ProductID=112
and I decided to get it (apparently it's only available in the UK at this point, at least that's all I could find, so shipping's a killer but . . . ). I LOVE it!!! It's a tandem (front/back) but seriously it's no bigger than a large single & it steers great (has bigger wheels which are great on uneven pavement). It does take up space in the car, but I think any double's going to, kwim? And the girls seem to really like riding in it. The main downside I saw in reviews was the lack of leg room for the back seat & it is TIGHT but doesn't seem to bother my kids at all, they fight over who gets to ride in the back seat (we take turns & added bonus, if back seat kid starts pulling hair or something we can switch them & the one whose hair was being pulled is happy about the switch. I did see a few on ebay when I was shopping but didn't want to wait around for one to come through that was cheaper than new. Since you've got time, you can watch ebay & also there's at least one yahoo stroller swap board I think (don't know the link) that you could watch. The front seat doesn't recline, so it wouldn't work for newborns, but is great once they're bigger. It's small enough that I don't mind pushing an empty stroller while the girls walk (or are slung, though that happens rarely now that they're older & I don't let them NIP, slings = nursing in their minds so I don't usually carry a sling anymore, still have some in the car, but not w/ me at all times like when they were little) The basket is small/hard to access but I just keep a mesh bag in the basket & if I'm shopping & need to carry things I pull the mesh bag out & hang it from the handles. And of course if one/both kids are walking then I throw my purse & such into the empty seat.
So, my recommendation would be to get the snap-n-go for the newborn phase & then the Marco when they're bigger.