upgrading home network need advice or opinions thanks

Okay, this is the new equipment i bought to upgrade my home network.

1. D-Link DIR-615 Wireless N router ---- Connected to D-link cable modem.
2. Linksys Wmp-600N Dual Band pci card adapter ---- For pc
3. Linksys Wpc-100 Range Plus Notebook adapter ---- For Laptop
4. Old equipment- belkin usb network adapter ---- 2nd pc
First, i would like to know if the pc i want to use to have my cable modem connected to is a bit old, it does not do 64bit only 32bit, i have windows 7 installed on it and am using the built in network card on the mother board. also, have only 1 gig of memory as well, wondering will this have anything to do with the cablemodem or the router running slow?
Right now i have a netgear G wireless router hooked up but my antenna snapped off and i also have plaster walls on the main floor of the house which is really interferring with signal. When i check my ps3 i have about 45-50% signal strength.
What i am trying to do is figure the best way to hook this all up. I have a total of 3 computers, 1 laptop, and a ps3 that will need to be connected to the router.
To get around the plaster walls i have come up with two different ways to do this.
1. I can bring my cable modem to the second floor and hook it up since i already have the comcast line in this particular room just have to switch the line at the box coming into the house from the main floor to the second floor.
2. I can drill a hole through the floor to the room below which i already have my cable modem connected and run the rj45 cable upstairs and put my wireless router there due to the second floor has regular dry wall not plaster walls.
I tested this last night with my laptop i went into the particular room with the laptop and the signal strength went from 2 bars all the way up to very good strength.So i know it will work just not sure which is the best way to do that part of this.
Once this is completed I will have the laptop connected with the new linksys wpc-100 rangeplus notebook adapter. I will have my pc connected to the network with the linksys wmp-600n pci adapter. I will have the 2nd pc connected with usb belkin wireless g adapter. Then the 3rd pc connected with rj45 from the router to the built in network card.
The ps3 i am still undecided, I know going hard wire from ps3 to the router would best but if i go wireless with the router being on the second floor as well with wireless the ps3 the signal strength will be very good. What is the breaker here is that i would have to run a long rj45 cable in the attic and drop the cable in the wall, i want to say it might be anywhere from 30-50 feet of cable, so i am not sure the distance will have a toll on the strength. This is why i am not sure to go wired or wireless?
can anyone help me out in anyway? thanks