Murali,
Upgrade the stock tubes to NOS 6H30P-DR and it will take the preamp to another level. Also, use isolation under the chassis.
Good ideas.
I shall look into the possibility of NOS tubes once the current tubes reach their end. In fact I have a very good tube advisor (Brent Jessee) from whom I had bought in the past 12AX7 and 12AT7 NOS tubes (Mullard, Telefunken, Amperex) for my VTL preamp (the Amperex Bugleboy 12AX7 with Mullard 12AT7 worked out as the best combination to my ears though the Telefunken gave the largest soundstage.
I use a Solid Tech Rack of Silence, one of the best racks available, for my hifi components and the ARC preamp is on the suspended shelf resting on Solid Tech's Feet of Silence. I don't think I can find a better isolation. I also use very good cables for power (VH Audio), interconnects and speakers (Audioquest).
cheers.
murali