Excellent advice - this is a great sounding amp with the stock tubes.
I think the stock GE 5654 are ok, but there certaintly are better tubes out there that will yield meaningful sonic improvements.
I do think it's a good idea to get familiar with your amp and stock tubes before venturing into the tube upgrade path, as it gives a better foundation for you to find the right sound that you prefer.
The link to the Yen Audio store's little dot upgrade tubes page: http://stores.ebay.com/Yen-Audio/Little-Dot-Tubes-/
Edited by Dept_of_Alchemy - 6/29/11 at 6:15pm