I need to select a router to install in each of our CO's to bring together a network of T-1 between our colos.
Look to Ebay or similar for 2500's with dual V.35. Either find them with DC supplies or buy DC supplies as spares. The DC version has only one inlet, but it is trivial to bridge an A/B supply with a diode bridge. We do so with our boxes. Depending on availability of DC supplies this could be very cost-effective.
The 2600's DC supplies are an exact mechanical fit and have a slightly heftier power rating and may be easier to find. They sometimes appear on EBAY as either 2500 or as 2600 supplies at $20 or less each. If you get stuck, the supply manufacturer sold us 20 of them at $65 each a few years ago. You may have to be persistant, and promise to never tease ci$co about it. Remember to load all 2500s with 16 meg DRAM and 8 meg of flash (or more). If you have a lot of 4 meg flash sticks, use 2 in 1/2 your routers (and say: PARTITION FLASH 1 8 - rather than 2 4 4), and new 8 megs in the rest.The DRAM is about $10 on ebay, and the FLASH is maybe $20. Try hard for Intel flash chips (or Sharp clones that ID themselves as "Intel") so you won't need to chase newer boot PLCCs if you get routers with old boot code than can't do AMD flash. Load them with unix compressed .Z images or see if you can find one of the kits that used to be around on the net to convert cisco run from FLASH images into more normal for cisco -mz gzipped types buried in a self extracting wrapper so your 25xx routers will behave like most other cisco routers. Find details in old C.D.S.C news archives. You can then load newer images onto a RUNNING router without the 2500 class B/S involving Flash-Load-Helper and remote disasters when flash is erased and tftp fails.