"Sollux seems introverted, being reluctant to talk to Kanaya and is the last troll to talk to the kids, as he saw it as juvenile. More evidence of this introversion is his shame at having once had an extremely immature argument with Karkat, which they both chose to delete from their chat logs out of embarrassment.... He is a well-known hacker, having a lot of experience with computer programs and programming... he has a penchant for bifurcation and duality, often splitting things into red and blue. In keeping with his zodiac theme, his appearance emphasizes duality."

(Taken from the Homestuck Wiki)

I'm looking for a lispy, stereotypical geek voice (nasally, lispy, slight rasp, possibly?), he would have a medium-pitched voice..