Upgrade my Theta Pro Basic lll

I am contemplating upgrading my Pro Basic lll to lllA status at a cost of $400. However, friends of mine are telling me that I am better off selling the lll and buying a used Gen.V or Va, the difference in sound quality is worth the extra bucks. Does anyone have expirence with these two units and are my friends right? My system consists of a CJ llA pre-amp, VTL 150 Amp, Silverline Sonata ll speakers, Theta universal 2 transport, audioquest volcano speaker cables and Tara ref. interconnects.
I have a 3a the difference is small. But you can get a 5a used around $1100.00. You should be able to sell your 3 and with the $400.00 for the upgrade get pretty close to the same money. For the same money the 5a is the clear choice.
I am a IIIa owner, but have not heard the non-a in comparision. However, from what I understand, a move to the Va would only be substantially better if you got the balanced version (and ran it that way), which costs more. The unbalanced version is basically the same unit as the IIIa in a buffed-up chassis. Good luck and happy listening.