Great and versatile setup you have there, but no wonder it’s quite heavy on CPU. Amplitube is arguable the worst, I’ve also been playing around with both Amplitube and Tonex and in my system avoid using them in live-situations, simply too heavy for my relatively modest laptop. I don’t know whether it’s the fancy GUI or other stuff, Amplitube is easily the heaviest amp sim I’ve ever come across. If you wish to try out some alternatives, Scuffham S-Gear has a 10-day free trial.
But enough about the guitar stuff, I’m mainly a keyboard player so I’ll provide my two cents.
Generally the Arturia stuff is good, so if you’re happy with what you’re getting out from them you could mostly stick with them. Some older versions of their synth plugins are notorious CPU-hogs, but I think they have improved on that front. It varies from plugin to plugin, but at least the newest version of the Jupiter is definitely not their worst.
Only plugin I would consider swapping right away is the Mellotron Strings, since you have a good free alternative: just download any freely available Mellotron sample pack (like SonicBloom) and load the samples into Kontakt. There may even be some packs available that are readily mapped for Kontakt if you search more carefully. You’re getting basically the same classic Mello-sounds without the added CPU-load the Arturia’s plugin with all it’s bells and whistles will surely add. Your “kontakt mellotron” won’t look as fancy, but it’ll surely be lighter.
Next thing to look at: optimizing the plugins. Reducing polyphony, dropping unnecessary built-in effects and adjusting sample rate and buffer size will all have effect on the CPU hit of each individual plugin. Since you’re playing in a live band setting, you can propably reduce the polyphony of V Piano quite drastically and still sound great. Try out different settings and listen critically. You might get away with much less detailed piano and rhodes sounds, they may even sound BETTER in the context than the hyper-realistic concert grand with all the symphatetic resonance magic filling the frequencies.
Same applies to synths: see how dense chords you’re actually playing with the JUP8 and OBX and choose the maximum polyphony accordingly.
And speaking of synths: what is your reason for using both the JUP8 and OBX? If we’re talking about bread-and-butter poly-analog stuff, is there a possibility that you might get away with using just one of the two? Of course they do have some differences, but very similar types of sounds can be achieved with both. And about the Moog: unless you absolutely need to have polyphonic moog-pads, always stick to the mono-mode! Most Minimoog-plugins turn into horrifying CPU-eating monsters when the polyphony is increased, and I think the Arturia Mini-V is no exception.
If still after all tweaking and optimizing your plugins of choice seem too heavy and you have some money to spare, here are my personal recommendations:
JUP8V → TAL-J-8. At least equally “authentic” sounding, lighter on CPU, freely scalable GUI (looks much better on smaller screens than any Arturia stuff).
OBX → discoDSP OB-XD. Used to be one of the best free poly-synths out there, now it’s commercial but very cheap. Much lighter than Arturia’s take on the OB.
B3 → GSI VB3-II OR AcousticSamples B-5. Both are affordable, lightweight and IMHO sound better than the Arturia. VB3 also comes with a separate GSi Rotary FX-plugin.
V Piano → Pianoteq. Physically modeled just like the Arturia, just more authentic, versatile and lighter on CPU. Can also cover rhodes, wurlitzer, harpsichord and plenty of others.
Minimoog V → The Legend. Best MiniMoog clone I’ve tried so far, and at least slightly lighter on CPU (unless you go crazy with polyphonic stuff).