The Pro-106 is the same radio as the PSR-500 and the Pro-197 is the same radio as the PSR-600. The guts are the same, but some of the buttons may be in different positions (RS likes the speaker in a different location so they had GRE move it for their models, causing the buttons to move around a bit). One thing to include in your price comparisons is what's included with the radio. RS sells the programming cable seperately, while GRE includes it with theres. Since the same cable works on several radios you may not need an additional one anyway, if you do include that in your price (since RS generally sells it at half off when you buy the radio, pick it up at the same time). For the portable models, you may get the AC adapter with the GRE model, while you probably won't with the RS version.
The PSR-800 is a different animal than the others you have listed. It includes the RR database on an updatable SD card so programming is generally much easier (just pick the desired system from the SD card and listen away). Rumors talk about a base/mobile version of the PSR-800 arriving soon. Just how soon isn't known, but if you prefer a base/mobile scanner (which it sounds like) it may be worth waiting for.