Audio Research VSi55 Tube Rolling

i am very happy with my new ARC VSi55 integrated amp, but have been thinking about trying a bit of tube rolling. the amp now has about 400 hours on it, and to this point i have only used the stock tubes.

i would very much appreciate specific suggestions that you might have. i am also interested to know if anyone has tried "cryoed" tubes in their VSi55.

FYI - speakers are coincident speaker tech partial eclipse II's, and CD player is musical fidelity A5.

thanks!