I was in the same situation as you last season - I'm 5'9" and 160 lbs, and I ended up riding a 151 cm Bataleon Airobic near the end of the season last year. Usually I ride between a 153 and 158, depending on what I'm in the mood for, but I honestly didn't feel like it was all that much worse. I probably also do a lot more freestyle than you, though, so it's hard to say, but I ended up going pretty fast through groomed snow and didn't have any problems (but again, very different boards).
My buddy last year also ended up getting a Skate Banana for super cheap, but it was way too short for him (149cm?), and he's only a bit lighter than I am, and about the same height. And he said it was fine.
I think the C2 153 cm is also a blunt-tipped board, right? I heard you can get blunt boards a little shorter than you usually would.
And yeah. How cheap?