In my humble opinion, the .1uf interstage coupling cap has greater impact. I think the 3.3uf Solen is a pretty nice sounding cap. You don't have to spend a ton of money either. I've had very good luck with these.
Thanks! I was hoping that might be the case. .1uF much easier to fit as some of the boutique 3.3uF are large. More importantly they are also large $ wise!