After several hours of reading and thinking over your opinions, I find that you are right. As said, I would opt for the X48 mainly because of the 16x16x PCIe CF feature, since its performance, even though better than that of the P45, would not be noticeable in real life (maybe a few more seconds to complete a task) and thus doesn't justify paying more money for a Rampage Formula. Since 2xGPU graphic cards have hit the market, even the 16x16x combo seems redundant (even though would be nice to be there).
So I decided to follow your advice on the PSU and I'll do the same on the mobo

. I find it reasonable to loose a few seconds (or a minute or two) in working with Winrar (I hope the differences won't be great when editing/converting HD video from HD Camcorder) and boost my graphics performance.
About the P5Q-E and Gigabyte solutions... I will overclock but not to the limit. I'm a complete stranger to overclocking but I'll get to it since it worths it. My main concern is stability. Do you ppl have any stability issues in mind concerning these 2 mobos? I read in a forum in thinkcomputers.com that some ppl had BIOS/memory issues with the P5Q-E. I swear this is my last question...before the next one!
In Gigabyte I like the easy-overclocking program while the 50,000 hours for the capacitors make me wonder why ASUS advertises the P5Q-E at 50,000 hours playing heavy games, 118,000 hours playing lighter games and many many more thousands when working with Office or other programs.
So, it will look like this:
P5Q-E or Gigabyte EP45-UD3P mobo
Intel Core2Quad 9550
Thermaltake heatsink with Noctua fan
4Gb OCZ Reaper DDR2-800
ASUS GTX-285 1024MB
Corsair 600W PSU
Blue-Ray Driver
DL DVDRW driver
1 Sata 320GB HD
...and an empty wallet lol.