150 sp isnt to bad you get 1 sp about every 2 or 3 guys. Also a 9 lvl gap would help cause i believe you gain sp 19% faster than 0 gap with the 9 lvl gap as opposed to 8% better than 0 gap with 8 lvl gap. Or what you could do is fight tons o monsters you can pwn in one hit you also get more items.
