I'm looking for some potent 10mm ammo like 200 gr. @ 1200 fps.  It's hard to find these days.  Everyone puts out dinky subsonic stuff that barely comes out of the barrel.  Where should I look?

Look into COR-BON.

Yep, it's hard to find good 10mm.  The reason for that is because it's kind of hard to handle at supersonic speeds.  Muzzle flip is supposed to be pretty bad, thoug I've never experienced it first hand.  Most of the stuff you find now is the 10mm FBI loads, which are almost identical to .40S&W and what .40S&W is based upon.

I can't find much in the way of 10mm where I live, which is why I didn't buy a 10mm pistol.

God Bless Texas

Winchester Silvertip is some of the hotter factory 10mm.  175 grains at about 1275 fps, and that bullet tends to expand to .81 in gelatin and keep its full mushroom.  It's a great round.  For self-defense carry use I'd look at some of the lighter Cor-bon loads, but the Silvertip is a great round.  Recoil is stiff but by no means uncontrollable out of a Glock 20.  Cor-bon's 135 and 150-grain loads are better carry loads, less chance of overpenetration.

Stay away from Hornady's 200-grain XTP; it's nice and hot, but doesn't expand worth a darn and will overpenetrate through almost anything.

I just bought some Pro-Load ammo for self-defense.  This is supposed to be some very accurate and reliable rounds.  I bought some 155 gr. @1350 fps for 627 ft. lbs.  I'm still looking for good strong practice rounds though.  I may have to get the Pro-Load target ammo.  It has similar ballistics but in a FMJ instead of hollowpoint.

Pro-load is also a very good choice.  I found that the Blazer 200-grain 10mm is a fairly good practice load, seems to be hot enough to give you some realistic practice.  Eric the Ammoman has 10mm Blazer at a fairly decent price.

Most potent stuff I've seen so far is [url]http://www.texas-ammo.com[/url]  They've got 200 grn @ 1250 fps. for a whopping 697 ft. lbs.!

10mm is a handloader's round. The factory stuff is downloaded to mid range velocities so you are not getting the round's full potential. This includes Corbon, that interestingly is nowhere near pushing their 135gr load (1450fps) to "+p" velocities in 10mm, which is AT LEAST 1550+. Maybe it had to do with corbon wanting to keep their claim that .400 corbon is faster.

People have clocked 135gr nosler handloads using imr 800x out of a 6" barreled G20 at 1700fps and 1600fps from a factory length barrel with no pressure signs.

... ditto