What tubes would you suggest for the following....

I have a pair of VAC Standard 220's with KT-88's. The tubes are marked VAC on them, but I have no idea what kind they are.

While I like the power and authority that they provide, I would appreciate any suggestions on alternate tubes to try to warm up the sound and move the sound more toward this side of "tubey". The amps now sound great, but lean more towards a solid state amp.

In short, I am trying to get some of the romance and magic that tubes can provide. My speakers are Genesis 501's.

I have read that ELECTRO-HARMONIX KT 88's are terrific, but was wondering if anyone has any other insights. It has also been suggested that I try the VALVE ART ones offered by ATSI (Advanced Tube Services).

thanks. Gerry