I just picked up PSP's "vintage warmer" plugin on a group buy. I am not affiliated with them in any way, but I just thought I'd share this.
It's like a anolog tape simulator (among other things) and sounds great on drums etc.
But I've also tried it on some solo strings using GPO and it sounds really nice! I've got a string quartet and a french horn and trumpet section behind my normal drums/bass/guitar etc etc (so it's NOT a classical piece) and I put all these instruments on a buss and added VW with some tweaked "fast tape preset" settings (eq's on 0, knee around 50%, mix around 70%, GR meters reading around -3db) and it fattens up the strings nicely! That and a little concert hall convo reverb with SIR, and it sounds great.
Just thought I'd share this.....