I'm not sure exactly what your asking, but I'll take a stab.
If you plan to buy a budget bike with the hopes of upgrading gradually over time, or as things break, be sure to buy a bike that is already setup with 9 speed components (assuming you're looking for a geared bike). That way, if your rear derailleur breaks, you can upgrade it with a nicer 9 sp. RD without having to replace the cassette and shifter at the same time.
Also, I'd look for the best frame I could get in that price range because the frame is the one part that you'll want to build around. Maybe something like a GF Cobia since the Cobia frame is essentially the same as the X-caliber and Paragon.
Also, you'll likely get better components and frame quality at a given price point if you can handle going with a rigid fork, at least to start. For example, an $800 bike w/a rigid fork should have better components and maybe a better frame material than an $800 bike with a sus. fork.