My issue is when i try and pickup the signal in the 2nd house its always too low to boost. What i was thinking is what if i used 2 or 3 extreme's, would my range be better?
Potentially, yes, but there would be no guarentee that it would. The reason is that the extending base station, whether it is an Express or an Extreme, would still have to receive a signal from the AirPort with enough bandwidth to extend in the second house. The extending AirPort would "boost" the signal strength, but not the level of bandwidth (overall speed) that it receives it ... so if the signal has low bandwidth, it can only extend it at this same bandwidth. Make sense?
Typically, this is where network designers would employ directional antennas/transceivers on both wireless access points ... but this option is a tad expensive, sometimes more so than the price of the base station itself.