Homestuck isn't a voice acted canon and I don't actually have much of a voice headcanon for him, but ehh, maybe something like Chad Sugg? That's a Tennessee accent, though, and Dave's from Houston.

Also since we've got a Rufioh, I'd be amiss not to link Dante Basco voicing a few of Dave's lines (cw: swearing, use of 'autistic' as a slur)