Building my new PC tomorrow, new to overclocking

That psu is WAY MORE than enough to handle a 4870 Crossfire.

However, That Mobo will not handle the 4870 Crossfire well.
I would recommend selling the 4870 when the time comes and getting a 4870x2 or GTX280 or whatever may be the top of the line card at the time.

The reason is that the PCIE-E Slots drop from 16x to 8x when you do Crossfire. In some cases, the 4850 gets limited. The Faster 4870 would be even more limited. The Result is that in some cases you could see a noted drop in performance if a game does not use CF well since each individual card would run slower than a single card.

The 4870x2 should never have that issue.

It's cool then, I can go without crossfire. What about overclocking my CPU?

well first thing is how good your mobo will be at overclocking it. first I would google the make and model of your mobo to see if its good for overclocking.

How exactly does my motherboard come into play when overclocking my CPU? Also will my RAM need to be overclocked as well?

this is really basic. have you read ANY overclocking guides??

I have that motherboard, it let me attain 3.6ghz with that processor and a Xiggy HDT S1283. The first thing you want to know is your VID, so download coretemp or realtemp.
Once you know that, you will use it as your first voltage. My Q6600 has a VID of 1.300V.
You will want to overclock in steps, so maybe 100mhz at a time. At each step, check your stability with prime95, if it passes after about 30 minutes or so, your probably ok. I was too impatient for this, so my first OC of the CPU was to 3ghz, or 333 x 9. It worked great at 1.30V.
So I stepped it up to 3.2ghz, or 400 x 8. It crashed after 10 minutes of prime 95, so I added voltage. Took it up .05V to 1.35V. It turned out to be stable. So I took it up to 3.4ghz, added voltage, yada yada.

Eventually, I was able to reach 3.6ghz (400 x 9) at 1.48125V. I don't leave it clocked that high though, because thats a lot of voltage and 3.2ghz its good enough for me. Just about as fast as the highest clocked CPU intel offers.

just up the FSB 10mhz each time.until the system gets unstable then up the vcore.