I'm currently using 12 guage speaker wire for the M60's and the VP150 and 18 guage for the QS8's.

I'm considering upgrading the QS8's to a thicker wire but I'm not sure how thick I should go.
The distance from QS8's to receiver is roughly 30 feet.

What is everyone else using for speaker wire?
Can you go too thick when using speaker wire?

Thanks,
Zak

You can't go too thick, except for the fact that it gets hard to work with. You should be fine with 14 or 16 gauge to the surrounds.

I used 12 gauge wire for the runs to my QS8s which are about the same distance as yours.

14ga Canare 4S11 for bi-amped M80 mains (15' each). 12ga Belden 5000UE for center (10') and surrounds (40' each).

All from Blue Jeans Cable.

With fancy-pants DIY techflex on the Canare from wirecare.com

I have Tara Labs Prism Omni 2 running in-wall to my Epic 80/500 system. It's 14 gauge and I'm very happy.

I'm a relative n00b on tech things but have never really considered anything higher than 12 gauge. I suspect you're fine.

14-12 gauge will do just about any household runs, if it is on the longer side then 12 gauge should be used. I would change out the 18 gauge on the surrounds for at least 14 if not 12. 12 gauge wiring from Monoprice is quite good and very inexpensive, there really isn't much reason to not use 12 gauge at their pricing.

Home depot also has a nice jacketed 12ga wire (two insulated stranded wires in a green jacket). I have a big roll of that sitting beside my receiver. One day I'll actually use it to replace the crappy wires I have now

I use 12 AWG for all my speakers, it is not hard to work with at all. My Qs8 runs are about 30ft as well.

12 AWG for mine as well (M60 fronts, VP150, and QS8s)... A bit overkill actually according to the charts online and the fact that my longest run is about 30 ft with most of mine around 20 feet, but the stuff is pretty cheap so who cares. It isn't like I am using that goofy $4,999 per foot stuff.

Zak, I use 16gauge lampcord for all my runs(none longer than about 30'). You sort of did it backwards; if you were going to use both 18ga and 12 ga, the 18ga should have gone on the closer M60s. An excellent explanation of speaker wire in general by a veteran audio professional, with a table of suggested gauges, is found here and is well-worth studying.