for serious?
no one can tell you what bike to get. but, do these things:
1) spend a few weeks to a month reading this forum
2) use the search
3) hit up your local bike shops
4) ride the bikes, ask a lot of questions.
doing these things you'll:
a) learn a lot
b) see about 2 threads per day pop up exactly like this
c) ?
d) profit!
This is what I did, and recently decided on a Surly Steamroller. I wouldn't really recommend a conversion if you're a noob, it's probably better to grab a $300-400+ bike off the shelf and go from there.