How 'selective' you need to be in deciding which router to mount in the table first really depends on how willing you are to end up with more than one router! A sweet deal on one that will bolt up 'quick and easy' isn't like to cover the entire range of features available in modern routers. That assumes that there is such a thing as the 'perfect router' in all catagories.
A general idea of HP required and Collet size (1/4 vs. 1/2) are more important than 'brand name' in my opinion. Just about any router will chop through softwood with a skinny bit, heck, my drill press doesn't mind doing the 'wimpy routing'.
The harder the wood, and the bigger the cutting edge in contact with the wood, the more horse power you need. Bits with a huge cutting surface and 1/4" collett can and do just snap if too much pressure is put on them.
I have never been sure enough about what I want in a router to spend more than 50 bucks on one, mostly because I haven't needed to. I started with an antique, all muscle, no frilly features machine made in the early 60's. I also ended up picking up a light duty Craftsman with a table and a bit set all for 50 bucks to help build a permanent table for the Millers Falls Antique.
Long term I'm thinking Porter Cable, Dewalt or Hitachi, but don't need anything they offer I don't already have, more than they wood cost.
I guess I'm just saying that until you make decisions on what it 'needs' to be able to do, it is impossible to pick the machine to do it. If all it needs to do is fit in the table without redrilling/replacing the mounting plate, by all means take the plate along shopping with you. Pawn shops seem to have a lot of Craftsman routers flow through them btw, or at least the ones arround here do. I just brought that up because they are a cash saving option where you can hold the plate right up to the router and see if the holes line up.
When checking that, it's worth a look to scan both sides of the base if the base plate isn't clear plastic. Alot of routers have more holes in the base than needed to attach the base plate. My craftsman is that way.
Good luck with your quest
wbh1963 is flowing with the grain in Arlington, Washington, USA
A day without curls is like a day without sunshine!