First, if you're not doing the work yourself, don't switch a piece at a time or even do a conversion at all. A piece at a time is not going to work 100% correct and even doing a correct 7 speed conversion will have it's hidden costs. (new bar tape, cable housing, cables, )

Second, build the bike based on what you need it for. If 7 or 8 speeds is enough, 10 isn't going to do you any more. And, it's going to cost you more because you will need more parts than just a shifter and downtube piece. (i.e. 10 speed cassette, chain, rear derailleur)

For what it's worth, I would say find some used 7 speed STI shifters on ebay or craigslist and then start looking for a bike co-op or a person that can do some work on the side. They really are not that hard to set up but the $180 seems a bit high to change the location/type of shifters.