Tigerwagji, going too fast
A well made SS amp can do vocals and strings equally good , I believe your setup is also good for vocals and string, no need to run after tube amps.Your system is hardly one month old, so give it some more time. I would suggest wait for at least six months or so. Enjoy the set up, try some room acoustics here and there, perhaps try some cables, say Mogami 2803 , VDH , Siltech.
Tube amps! You will be disappointed if you buy anything under Rs 50K. Good tube amps are prohibitively expensive!
There is a lot of talk on this forum about Lyrita SET amp ( some Rs 60K affair) but with hardly 3WPC you will need high efficiency speakers (91 db +) , means you need to upgrade for speakers too.
If at all you are so keen in upgrading, consider a mid-way solution (best of both worlds) Hybrid amp (tube at pre stage , SS/ MOSFET at power stage) , check Jolida Hybrid (1501 RC?) at Oceanic Pune. I had that(excellent) amp for sometime (before I upgraded to Cadence VA-1)
Another approach could be, wait- save and the go for tube based stand alone pre-amp + Solid state Power amp. Check with Acoustic Portrait, you might find a deal (even their Pre+ Power combo is damn good for the price) .