New to dirt bikes,, rode quads my whole life

1) your physical size (both height and weight are important)
5'11" 250lbs
2) How physical / aggressive are you ?
not extremely aggressive
3) what do you plan to ride- MX/SX tracks, woods, fields with friends or ?????
mostly trails and woods
4) Do you have any riding experience?
only quads
5) Do you think you will race ?
no
6) Are you mechanically inclined and will you be doing your own bike work?
i can figure out just about anything with the help of a good fix it book
7) Do YOU have a preferance to a brand/ motor choice (2 or 4 stroke)?
i prefer 4 strokes on my quads
8) Do you have a dealer close by your home that you might use and what brand(s) does he carry?
they carry honda, kawi, suzuki, yamaha, but probably will be buying used
9) How much ($) do you plan to spend on a bike?
up to about 16-1800
10) Do you live in California?
nope, FL
11) Your age?
28
12) anything else that you think would help form an opinion
not really

just wondering what would be a good sized engine for me. i found a 94 cr250 for $1100 and a 04 drz125 for $850 on craigslist. i would like a newer bike but i'm not sure if the 125 is strain to much with 250lbs on it

i cant find a single xr400 for sale within 200 miles of where i live. but i did find a 2002 dr 400 for $1600 from a local dealer.

I also found a 2000 YZ250 for $1700. is this a good bike? does that price seem to low (as in something is wrong with it)?