Replacement valves for icon stereo 25mk1

[rivendell]

Hope someone can give me some pointers to the following questions.

I have an ICON Stereo 25 and now that ive been listening to the valves since July, i would like to get some alternative valves and start tube rolling, my musical taste is very very varied, the amp is hooked up to Celestion A3 loudspeakers, with Musical Fidelity M1A DAC, PC and hard drives, all cables including usb are Nordost All music is FLAC File.

1. Can any suggest a good quality replacement valves? the EL34's and 12AX's fitted are really nice, very detailed good mid, and great bass but i just feel that there is more i could get out of the amp and improve the sound. Not too bothered about the budget, would £200-250 get me some nice valves?

2. If i choose to replace say the existing valves with the same type ie EL34 but from a different manufacturer, do i have to rebias the amp? I know that i will have to if i choose an alternative valve i.e KT88

3. I have never had to rebias and amp before, should i leave well alone and get someone who knows what there doing to do it for me?

4. I live in central Scotland can anyone recommend someone who is competent to carry out this work for me

Looking forward to your comments