Window World (they usually have coupons or specials in the Clipper magazine/on their website)
Pella Windows
DunRite - Sharpsburg (Dino is the contact person)
Thermo Twin - Oakmont (positive and negative reviews)
Steve (412) 537-7572 (30 + yrs experience; fully insured; free estimates)
Advanced Window and Door (412) 751-1001 (Steve is the contact)
Again, thank you to everyone who responded. This "budget mama" appreciates it. :)