Yep. I have more questions. I would like to get another bike some time soon, possibly mid-to-late July. I am thinking of getting a road bike that would be capable of commuting, light touring, and going fast

. Since I am using my bike as my primary form of transportation, I would be keeping both bikes - right tool for the right job, ya know. Or at least plan B
I would like to be able to use move the pair of wheels between the bikes, to which ever I am using more frequently. Ultimately I would like to have a quality set of wheels on each bike, however this seems somewhat cost prohibitive at the time being. Maybe a good winter project. I think being the new bike will be stretching the wallet a little, so I've been putting in as much OT as I can find on the weekends.
I am looking at maybe a Cannondale Synapse 5 sport (the sport models have eyeleys for racks and fenders, etc), which I can get (semi) locally for around 1400 I think. It has 105 level components, and is supposed to have a very good ride. It's also supposed to be pretty easy to switch in and out of a more aggressive riding position, although I suspect this is true of any road bike. I have also considered the LHT, but to be honest I'm not really feeling the bike. I will try to give a test drive before I write it off completely though. I haven't riden the Cannondale either - just window shopping atm.
ANYWAY, what I mean to ask is two things. First about the hubs, if I am planning on getting a road bike and would like to use the same wheelset, would I be better off getting a road hub versus the mountain, due to the spacing? As I understand it, the narrower road hubs could be used in a wider fork with a longer axel/skewer and some spacers on the ends. Or, how easy is it get a mtb hub on a road bike?
Secondly, a large part of the reason I want to get a second bike is that I think my 7.2fx is too small for me. I tried both 17.5" and 20" frames, and found the 17.5" to be more comfortable in the store. However now that I'm riding everyday and more comfortable on the bike, I find that I want to stretch out more. It's too late to take it back, so I want to do what I can to make it fit better. My ride to work is short, and I am not expeirencing any discomfort, but I am concerned about longer rides. At 6', I think I'm just a on the big end for this bike.
Any suggestions? New handbars(I would like to get bullhorns, but failing that an actual flat bar with bar ends), a new stem perhaps? I read that some people move their seats back some, but I worry about putting undue stress on the seat post at my large size.