Have you read this guide?
http://www.silkroadforums.com/viewtopic.php?t=1243
I found it very helpful. Made level 16 fairly quick. You don't HAVE to get a sos bow to farm the Bandit Archers. Level 16 NPC bow, 7 in Pacheon Mastery + 2nd lvl Anti-demon missle + 7 mastery of any Force Imbue = Bandit Archer dead in two hits... one hit with a Critical. I found a lvl 16, 7 Critical bow in a stall for 18k and it increased one-shot kills a lot.
Click on Archer > activate imbue > start attack with anti-demon > target next archer while your character is still attacking the first> rinse and repeat. Sure a +x bow would speed it up, but it works pretty good without one. By camping in a corner in the center tower, I can get 100 sp in 50-60 minutes... including grabbing most of the gold. Don't know how that compares with using sos gear, but it's good enough for now, for me.