Get the first 'Big Red Book' from the GAL, and look up William Allen's article 'The Basics of Air Resonance'. He made measurements of air modes on different boxes with holes in different places, and made sense of it all in a very useful way.
Moving the soundhole down toward the middle of the box will raise the pitch of the 'main air' resonance somewhat. This is the lowest pitched resonance that can actually put out sound effectively, and has a lot to do with how the lowest notes sound. If my experience is any guide, the move you've made will have a noticable 'brightening' effect on the low range. There are a couple of things you might be able to do to recover.
If you haven't already cut the hole out, make it a bit smaller than usual. This will leaver a wide margin on the rosette, but that's not so bad. It's also easy enough to enlarge the hole later if you want.
You might try making the body a shade deeper; even an extra 1/4"-3/8" can make a difference. This doesn't so much drop the final air mode pitch as it does 'smooth out' and broaden the resonance, spreasding it over a bit wider pitch band. This makes the bass tone a bit 'darker' to a lot of folks.
The easiest way to get a 'bassier' responce is often to 'tune' the main back resonance to something like a semitone higher than the 'main top' tap tone pitch once the guitar is assembled. On most guitars you end up shaving braces to do this. The nice thing about it is tha it brings up the bass without altering the treble at all, as thinning the top or scalloping the top braces will. It's also structurally less ofa problem.
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