When you buy drywall anchors the boxes have weight ratings on them now, the medium ones(#8 screws?) are rated for ~30lbs per anchor, you should be fine.

I recently watched a show where they tested the holding power of all the various types of products available to mount pictures etc. to drywall and the ratings were quite accurate. IIRC toggle bolts held 100lbs before breaking out of the drywall.

Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70