there are a few reasons for crossing the fronts.. For example, the lower ranges are the most difficult to reproduce {power wise}, so if you have 80 watts per channel, instead of only leaving 40 of them to power from 100hz to 20Khz you can have the entire 80 and let the sub do what the towers could never do... Now you may say "but let the fronts help the sub", that is not a good idea for a few reasons, mixing bass from your fronts and your sub sounds cluttered and will do a good job of muddying up your low end for no reason, freeing up the power from the mains will clean up the mids and highs from the front end, a 300 watt 12" sub taking care of the 80 and down range will produce much better bass than a 5 1/4" tower driver covering from 30hz to 5K and getting 30 watts to do it not to mention most subs will go sub 20hz without much trouble...
So no overlapping, free up the power, and clean up the top end...
As far as outgrowing an HTIB setup, you have to start somewhere, most people that come one here asking for advice on what system to buy are coming from a small sat system, and then are amazed when they see what you can get for a little more money.. I honestly think the HTIB guys end up with a better system that the guys that start off with an entry level system, the entry level systems satisfy them and they will never upgrade, an htib leaves you wanting more and not wanting to make the same mistake twice so you normally buy something at the top of your budget...
