Yeah, you got Voodoo and Alcatraz as the big club nights, but there's smaller (cheaper) nights like Aztec, Monkey Business and Gimp Fist who play house and techno as well. I only returned to Liverpool myself at Christmas (was living in Spain) and I'm really excited about the amount of good quality club nights around.
I saw Speedy J and RNG last weekend, and in the next few weeks I'm going to see Magda, and Oliver Ho. Nice!
www.outlar.com is a great resource for info.