performance question.

hi , just confused with a setup of repeating site configuration. Have a 4Mbps dedicated connection that is going to be served on 4 sites. main station has a p4 pc with 256mb ram, 4 ports ethernet and 4 mpci, 1 for omni and the other 3 for grid antennas. Im planning to use RB133s on other 3 sites, the question is should i repeat the signal from the 2nd mpci that connected to omni, or insert another card for backhaul to carry the signal from the 2nd to 3rd etc. How does this two configurations effects the performance & load on cards ?

What wattage of mpci cards?