Yoshimi: http://yoshimi.sourceforge.net/ is a fork off the zynaddsubfx code tree.
If you could have only one vst this might be the one. Yes, like it’s parent zynaddsubfx it’s a beast. However, for sheer sonic capabilities the two are hard to beat and well worth the learning curve. The feature listing on the Yoshimi homepage reveals more about it’s incredible array of features.
As a diehard linux user (ubuntu-based) I appreciate that the current version of Yoshimi can be installed using a package manager. There are tons of presets available (installable using the package manager as well). The developers also provide native install packages for practically every mainstream linux distro out there, .deb, .yum, .rpm, etc.
I found Yoshimi to have excellent sound quality, responsive controls and not too hard on the cpu. Complex presets can push up the cycles but nothing terrible. Like the YFM262 and YF2612 vsts I posted about earlier Yoshimi runs standalone and flawlessly in Renoise.
I hope you’ll check it out and may find it useful. Cheers.