My recommendations:
Gigabyte Choices:
P45-UD3L (no RAID,CrossFire,etc)
P45-UD3R (RAID)
P45-UD3P (RAID,CrosFire)
ASUS choices:
P45-P5Q (RAID)
P45-P5Q Pro (RAID, CrossFire)
All the above boards are less than $140 WITHOUT MIRs. It's lower with MIRs. Prices based on Newegg.
Out of the above option's I would get the P45-UD3P (If you plan to get a 4830 or other ATI card.
P45-UD3L or P45-P5Q if you plan to go with a 9800GT,etc.
Also note, that before upgrading your GPU if your PSU is low quality,etc look in to upgrading that first.
@OP: Please list PSU, case,etc.