We have 6 month old twins who will outgrow their infant car seats in about 2 pounds. We purchased the eddie bauer 3 in 1 convertible car seats so we can still have rear facing and then graduate when needed. We can't get these seats to fit in our 96 dodge caravan. The problem is there is not enough space needed for these seats to recline properly. We have them positioned in the 2 bucket seats behind the front seats (there is no way that we could fit them in the rear) and when they are fully reclined (as it says they should be for rear facing) the front seats are jammed up against them and the marks indicating "level with ground" aren't even close to being level. I would have to remove the front seats or sit with them at the dash to accomplish this. The drivers seat is at the max for me to be able to drive (comfortably away from steering wheel) and my husband (who is 6 foot 5 inches) would never be able to drive the van as we couldn't put the seat back. I don't know what I'm doing wrong???? Do I have to buy different seats or a new van? I don't think that we could even put these seats in our Yukon as there isn't enough room there either. We also use the Yukon to haul our boat for family outings so we would need to be able to transfer the seat from the van to the truck. Please help if you can.
As another poster mentioned, try taking the base off the 3-in-1 (instructions are in the manual). Without its base, it is one of the less 'greedy' seats in terms of the front-to-back space it requires. We own two Alpha Omega seats, and they make decent rear facing seats (in our experience), and fit even in our (small) '96 Corolla at newborn recline angle, without putting the driver or front seat passenger up on the dashboard. When we first got the AO, we tried it with the base, and figured we would have to return the darn thing, since there was no way it would fit in the Corolla that way.
That being said, the warnings you received about the seat are also valid -- it is NOT the only seat you will ever need, it has a relatively low top harness position (the top headrest position CANNOT be used with the harness), and it makes a rotten booster.
Another poster recommended the Marathon and the Radian as other possibilities, but I would worry that these may also cause you trouble at the newborn recline angle, as they are both tall seats (quite a bit taller than the AO without its base). The Marathon (and other related Britax seats) are up on a base, so they take up a lot of front-to-back space when at that angle. The Radian is not on a base, but it is a really tall seat, and it has an enforced rear-facing recline angle (difficult to install it more upright in many vehicles) which just makes it take up a lot of front-to-back space when rear-facing. For example, I can only install it RF in our Corolla in the center position, sort of protruding forward between the two front seat backrests; in either outboard position, the front vehicle seats can't even move up far enough to clear the Radian.
I just went back and saw that your children are already 6 months old, and will probably be somewhat older still by the time you move them into convertibles -- at that point they probably won't need the newborn (45 degree) recline angle, and the Marathon and its relatives would definitely be worth considering. It is relatively easy to install those seats more upright for older rear-facing children, and they'll give you a lot more use for the money than a 3-in-1.
Katrin