What could you get with $300?

Gigabyte EP45-UD3P (open box $93/NIB $135) + E8500 or Q6600 ($190/$198)

I would get the UD3P and a Q9400.

EP45 UD3P, and i'd squeeze together the cash to get a Q9550

if not a Q9400 is fine. microcenter usually has them on sale

Gigabyte EP45-UD3P and an E8400 (overclocked to 4.4 on air) - Gaming/interwebz

Or

Gigabyte EP45-UD3P and a Q6600 (overclocked to about 3.4 on air these days) - Encoding/photoshop

It depends on what you want to use it for.

Gigabyte EP45-UD3P, and a Q9550 for sure. That is if you can squeeze the cash for the Q9550. If not then a E8400/E8500/E8600 would be plenty fine if you overclocked it high enough.

Edit: how could I forget the legendary Q6600, that is also a possibility.

P5Q-pro Openbox and a q9550

Mainly cause that open box saves only puts you 60 something down the hole and not 90 something for the gigabyte openbox i believe.

UD3P and a E8400 overclocks like mad and gets you in the price range you need.

The Gift of friendship

Or seriously a gigabyte p45 with a E8500 or e8400+xigmatech cooler

Intel E8500 cpu and Gigabyte UD3R mobo combo, $294.98
($15.00 mail in rebate)
http://www.newegg.com/Product/ComboD...t=Combo.173019

I would probably get the Gigabyte GA-EP45-UD3R and the q6600(assuming it's a low vid and G0). That comes out to be $299.98 not including the $10 mir.