There are also drop bar bar ends (I think Origin 8 has some), if you can imagine that, but I would think a wider off-road drop would be more pleasing.
TT bars on a true off-road ride where you would want/need wide bars might be problematic as a safety issue.
For OSP stuff, off-road drops should be fine.
Salsa Cycles | Components
I think you can pick up a 26er frame and do the same thing, for cheaper than a 29er. You may have backup parts already that you can use. Run disc and you should even be able to stuff 700c rims with road slicks on it, as they will be similar to a 26" wheel or even smaller than a 26" wheel with 2.3 on it.
If you want to go CX, I would invest in a CX setup.
As for CX vs road, this sums up my beliefs. Can I use a cyclocross bike for regular road-biking purposes? - Bicycles Basically who cares unless you are hardcore road racer. The geo is so similar it doesn't matter much, and CX geo will likely be more stable at speed due to a slightly longer wheelbase and slightly longer chainstays. Although going high speed on tiny road slicks seems counter-intuitive to safety.
Edit: Bike Porn, but way outside your budget of $500. Picture after initial assembly prior to testing and refitting/tweaking parts.
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