imho, it doesn't seem 200 pounds is too much for any given frame, per se. if you're concerned about anything, it should be your wheels. lots of the bladed spoke fancy pants wheels have weight limits, which you would want to be aware of. stick with something 32 or 36 spoke to be safe.
if you plan on eventually competing, you should invest in which ever bike is required for which ever competition is most interesting to you. obviously cross racing is the best and super fun, but not for everyone. i've only raced track and cross, but the general attitude at a cross race is much more laid back and more fun oriented.
i'm sure if there is cross racing in your area, there are clinics and practice days and so forth. perhaps there are also group road rides of your caliber from a lbs, which would be a great way to meet other riders, learn good routes, etc. throw some slicks on a cross bike and you pretty much have a road bike!
if you're on a budget, you could consider buying used or picking up something from
www.bikesdirect.com. however, as you are aware, fit is critical. you may want to get a general idea of your fit by going through one of the various fit calculators. this one is good:
http://www.competitivecyclist.com/za...LCULATOR_INTRO
a lbs can help fit you to your new bike, which helps justify the higher cost. also, if you're a beginner, bicycle mechanics may be quite challenging, aside from requiring tools. a used bike may require some tweaking. a bikesdirect bike requires some assembly and tuning. either situation could also mean a trip to your lbs for help, which would be a hidden cost. a lbs would have your bike ready to ride and can be a point of contact for future repairs and so forth.