Diamond S has nice stuff but it's not cheap.... how much are a set of A-arms going for $800.00 - $1000.00 ? I think for stock ride quality your best bet is MPI with arms,spindles and pins for the 12lb weight loss and solid construction without twitchy trail manners or ball joint issues.... just my .02
Before you drop your coin on an MPI front end. PM ColoradoYamaha. I'll let him fill you in on all he's had to do to keep his on the snow. MPI makes some great products and some not so great products. I've seen this one first hand and I'd say send the PM.
Mountain Mod seats are awesome.
I have the Timbersled BarkBuster on my SC Apex for 2k + miles and have had zero issues. That said I don't ride trails much so maybe thats why I Love mine and would reccommend it to anyone.