Handgunr, I'll tell you what I've found out since I first posted this thread and what options there are for a semi-auto hunting handgun. These are current production firearms with the various solutions to get them ready for game hunting... Which is best? I don't know really and still haven't decided on one for myself.
10mm: With McNett's loads, this thing roars. He has a load of 200gr xtps out of a Glock 20 4.6" barrel at over 1200fps. A guy on Glock Talk used a Dan Wesson RZ-10 to take a nice sized elk with a 180gr gold dot. It was broadside shot and the bullet penetrated fully at 90~ yards. Guns available here are the Glock 20, DW Razorback, and the Witness. What I've seen, the Witness isn't very accurate and has questionable build for full-power loads. You'll need to buy a 20-22lb recoil spring for it out of the box. Glock 20 is a good option, accurate with tons of aftermarket barrels and parts. You might need to install a heftier recoil spring in it as well. Razorback has had nothing but glowing reports, I reckon it's good to go out of the box and is accurate.
.45 Super: This is basically a .45acp with higher pressures and will chamber in any current .45acp gun made. Velocities push a 230gr bullet from a 5" barrel at 1200fps and a 250gr at 1000-1100fps. You'll need to beef up springs in the 20lb range if you want to use it, pistols like the Ruger P90, Glock, HK USP, and Sig P220 should handle it fine. 1911's will need the heavier recoil spring plus a EGW firing pin stop, and a possible heavier mainspring. All are to slow down slide velocities. Texas Ammunition makes the ammo for those not wanting to reload.
.460 Rowland: Longer .45 Super loaded to higher pressures. Clark is the only one who sales the barrel/recoil spring combo and recommends use in only mainstream 1911 guns (but approves RIA 1911s from what I hear). Velocities to expect are around 1350fps for a 230gr bullet. Ammo is available from Georgia Arms.
.400 Corbon: Any .45 pistols you can get a conversion barrel for will work. EFK Firedragon has ones for all the firearms mentioned under the .45 Super. This cartridge approaches 10mm velocities but isn't quite there. Highest load I've seen is for the 180gr bullet at 1200fps, or about 150fps slower than the 10mm. I don't really know if using this cartridge is even needed if you can shoot the .45 Super. Once again, beef up the springs. Ammo is available from Corbon, but at slower speeds.
.40 Super: EFK has barrels for this cartridge in the above mentioned guns as well. This is a necked down .45 Win Mag cut to 10mm length and pushes a 200gr bullet over 1300fps. Only problem is, it's strictly a handloading affair, the hard way. Brass is no longer made, so Starline's .45 Win Mag brass will need to be reformed. Dies from Redding are $60 (RCBS wants $100+ for a 2 die set
) and you can size the brass is one run, then trim. Load data is hard to come by, but the guys on the reloading forum over at Glock Talk have experience and can give you the load information you need for the cartridge. It may currently be a wildcat, but it leaves the 10mm behind in velocities at normal pressures.
Ever since I started this thread, I have basicly narrowed down my current firearm choice to the Glock 20, Ruger P90, or RIA 1911 (dropped 10xx Smith idea due to lack of aftermarket support). All three fall within my budget and can shoot one of the above listed cartridges out of the box with just a spring change. I still have reservations about the Glock trigger for hunting. If I go with a .45, I might eventually grab a .40 Super barrel and go from there. Glocks still can't use lead bullets very well, soft bullets leave a lead ring in the barrel and cause (bad) problems. Aftermarket barrels solve it though. I'll be shooting them but bought and not mine, much more economical than jacketed ammo and as you stated, good for smaller game. Thanks for the nice comments on my site as well.