Hiya!
Lanliss...you're an Old Grognard like me, aren't you? Remember back in 1e or Basic days? Getting XP for killing was 'minor' and getting XP for recovery of treasure was 'major'. Then tack on some of the optional stuff found here and there in Dragon mag, or on a BBS or FTP site (remember those?) for things like finishing some particular goal, or finishing the module. Go back to that way.
This is one of my preferred methods. It rewards "play style"; from players who like to go in guns-a-blazin', killing everything that moves, to players who like to take a measured mix of combat, stealth, and diplomacy, to players who like to avoid combat if at all possible and *just* use stealth/role-playing. By giving XP for GP (whatever ratio you decide; I use 1:1, but I'm kind of a stingy DM..."miserly", even...), the players method matters most.
Does it make sense that a fighter gets better swinging a sword if they get all stealthy? Nope...but so what? It's a game, after all, and as long as the DM explains the reasoning behind the 'leveling' method (honestly, gaining 'levels' doesn't make much sense to begin with), most players can see, understand and accept (if not grow to prefer) the "XP for GP" method of ye olden days.
^_^
Paul L. Ming