First I suggest getting to a range that rents guns and trying a lot of guns. A two gun sample is too small to figure much out. It is very possible what you liked were the platforms, or the combination of platform and caliber, and not just the caliber. If this is the case, you may get something else in that caliber and be very disappointed. Or you may like the caliber. You won't really know until you try other guns.
There are a few good guns in the ~$400 price range, but not many good .45s. If you like a bigger caliber, try the .40S&W, if you like it you will open up many more options.
As for your stated choices, I wouldn't necessarily suggest any of them (I don't know enough about the Witness to comment about it).
Hi Points can be reliable, but they are cheap guns with poor ergonomics. Fine for just for the heck of it after buying other guns, or if you can't afford anything else. As an only gun when you can swing something else, I wouldn't suggest it.
If you want a Ruger .45ACP get the P/KP90 or the discontinued P97. For my evaluation of the KP345 see my next post (I edited it out to make this post more managable).
I love Taurus. I think the 24/7 is a great design. If you were looking for a 9mm or a .40 I'd endorse this one. However, they have had some issues with the 24/7 in .45ACP (it seems that nearly all of the problems I've ever heard of with this pistol were .45ACP). If you want a .45 and a Taurus, check out the PT945. The PT1911 may be a little more than you want to spend, but if you see one near your limit, grab it.
The Glock? Nothing wrong with it, but it is far over your limit. If you'll change your limit for the Glock, there are a lot of other guns you should consider.
My suggestion if after trying some other guns you still want a .45ACP:
-Consider used guns. That may put some S&Ws, SIGs, Glocks, Springfields, Kimbers and other higher quality brands in your price range.
-Rock Island Armory 1911. I don't have one but I hear a lot of praise for it.
-Charles Daly 1911. They can be hit or miss, but I am well over 10K rounds through mine and through most of its life it has been reliable enough to load up as my bedside gun on occasion (when the reliablity goes down, all it has needed so far was new springs).
-As I said above: Ruger P90, Ruger P97 (used only), Taurus PT945 (though make sure it fits your hand) and Taurus PT1911 (if you can find one in your price range)
