Hi jack, you have a couple of options:
1. use an ethernet cable which can be up to 100 meters long - but that may not be so practical.
2. use a booster that you install appr. in the middle between the router and the upstairs PC. They cost around $50.
3. convert to N protocol which has a much better range. But that would require a different router and an N dongle for the remote PCs.

ya the ethernet cable wouldn't work and i'm not sure if i could put a booster in the middle. N might be the better option but not sure when we could set it up.

I would think that 2 of the same would not change anything. The range of each stays the same. It's not like 2 locomotives in front of a train. Your problem is range and that you can only improve with either a range booster or another technology like the N protocol.

If you have a router closer by the system, that would help. But then you need to have a phone outlet and a modem handy. If that is the case, no real problem except for possible interference. But that can be managed.