Well you are on the right track. What is your budget? would you prefer new or is 2nd hand fine?
Many will say you need a hardtail to learn on and i'd say this is true too but i've seen you ride and i reckon you should be ok if you don't really want one.
The DH3 is an ok frame but unless it has a Fox Vanilla RC fitted to it as many people did I wouldn't bother as the shock they are sold with is pretty crap. I'm not too keen on the horizontal dropouts on it either. Was a bad idea an you really need to convert your hub from QR to a bolted axle to avoid it slipping. Not bad for the money though mind
The Bit Hit Comp is pretty good, shame it's not the expert model but they are still pretty good. They actually have 6.2" to 7.5" travel which aint bad. You can actually upgrade the frames to the expert spec with 6.8" or 8.1" using a longer stroke shock and the expert plates. Infact you can even go as far as 9" with custom plates:
http://www.avalanchedownhillracing.com/bighitlink.html
The 24" wheels on the old model is a bit anoying though mind. Betd do make a 26" rear end but i'd probably avoid this frame if possible and get something where you could keep your current rear wheel.
Soon as you give me your max budget i'll have hunt for you.