Audio Research V70 or VS55 power amp

I've got the V70 power amp, and have the chance to buy a VS55 (but can't audition it).
The VS55 seems a bargain, but only if it improves my existing amp! I'm using Proac 1027BE floor standers, and a ARC LS2B preamp.
I don't have any particular problems with the V70, apart from a "ticking" noise from fans, but always looking for improvements!
Any thoughts?