If you want to have a sump (and you should), you really should (and I mean really) look into the ATI Bubble Master 160. It's powerful with a very small footprint--8" x 8". You won't be able to find anything with a smaller footprint for a corner tank, that can pump 900 lph of air.
If you've never used a high end skimmer, the 160 might present you with some new learning curves, but it's worth it. The 160's are notorious for dialing in troubles when new (or in new systems), but after they get set, most rave over them.
At $500, it's a little over your budget, but it's really, really worth it...
Another option for tiny and powerful are the Bubble King Minis--but they start at just under $900...! Also the Tunze's are very adequate skimmers with even tinier footprints, but even though they share the same pump with the BM 160, they are much less powerful (actually Tunze refers to them as "gentle"). The BM 160 packs a whole lotta punch with it's meshwheel design, in very little space....!
And check around the used equipment forums here on RC. I am thinking of setting up a 92g corner tank as well, and just bought a 9 month old used BM 160 here for a little over $300. You can save by buying slightly used...!