I don't think tubes will make that kind of drastic change for you but you can look at JJ's or Tung Sols, with the latter being significantly brighter.

I suggest JJ in the Power section, and for the Preamp. In my AC30 CC1 i use a Tung Sol in the first gain stage, giving you the clean, bright sound in the normal input, with NOS RFT's in the phase inverter and 2nd gain stage (bright channel). These tubes are a lil darker, and i find they smooth out the tone, especially on the heavier gain side, which really rekindled my love for the AC30, as i was going for a more Blues-Rock tone.
Plus, these tube suggestions came with help from Cathbard, so i'm sure its a trustworthy opinion, he's got more tubes than the London Underground.