I have a lot of equipment that is worth $$ but the only merchants I meet have only 1200 or less cash on hand. Where xan i sell my good stuff? I really haven't been paying attentio I guess until now, but I am losing a lot of money!

Which game are you talking about? Morrowind?

1200 or less? Sounds like Oblivion. If your mercantile skill is high enough, you can invest in a shop to permanently increase the merchant's capital. I can't tell you the richest mercahnts, as i honestly don't know. One can get a general indication of a store's quality (and therefore $$$) by listening to the random comments.

Though if it were me, i'd not be too concerned about selling 5000 septim stuff at 800 or so. Why? Once your level reaches the high teens, the poor ass bandits (even the smeggin' peasants!) are toting ebony, glass and daedric gear. What you may lose in value, you'll most certainly gain in the sheer number of items you'll be picking up.

The last thieves guild fence has the most money I've seen; 1500.

Some of the traders in the market distric have 1200 and fairly low mercantile skill, allowing you to haggle a bit. Unfortunately that doesnt help with the really expensive gear.