If you have done a good bit of reading and looking at prints and you feel like its going to rock your boat, I think you'd be doing yourself a disservice not going for it. It might be worth it trying cheaper (relatively) methods (used camera and lenses etc) to confirm that it does rock your boat before actually going the whole nine yards. LF equipment (especially used) tends to hold its value reasonably well, so if you feel it does not work for you, you can sell everything without taking too much of a jab in the gut.
Having said that, I'd think a bit about the exact format you'd like to go with. The consensus seems to be that 4x5 and 5x7 are quite similar in terms of weight, bulk, travel etc. 8x10/7x17 is a quantum jump, and 11x14/8x20/12x20 is yet another quantum jump. There is an advantage to shotting the largest format compatible with what you want to do in the sense that you can always slap a reducing back on it to shoot smaller formats. But if the equipment gets in the way of what you are trying to do, its not worth it.
Good luck, DJ