Need advice for my Jolida 302BRC

Hi all,

I want to get the most bang for my back with some modifications for my Jolida 302b. Should I:

(a) replace the stock tubes
or
(b) do one of the many upgrades available (factor, UnderwoodHiFi, etc)

I've been quite happy with the amp. What I would like to get out of the upgrade is more pronounced base, and I guess a little better defined soundstage.

Any ideas would be VERY, VERY appreciated.

Thanks -- Marty