For my house wiring, the 20 A circuit is dedicated (only the audio outlets, 4 WattGate). They are "star" wired. Yes, the AC+, AC- and ground all run directly back to the circuit breaker panel. The house is grounded with 2 ten foot copper rods and is also tied to the cold water pipes. The breaker panel is 220V, so there are AC breaker on both sides of the 220V (different phases). I made sure that the heavy duty equipment in the house is on the other phase from the audio gear to further isolate it.
Sounds like you need AC isolation (such as the ultimate outlet, it will remove the nasty noise from other devices on the same circuit). The Thor would also allow all devices to operate from the same power and ground (but it is quite expensive and will not help if the ground is not good).
If you converted from 2 wire to 3 wire plugs .... do tell ... where did you get the ground wire??
If you are getting radio reception through the Io, try some shielding to get rid of the noise (such as cryotweaks http://www.cryotweaks.com/product.asp?pf_id=ERS).
For tubes, search around, there is plenty written up. From my experience the best bet is Telefunken ECC83 (12AX7) in the V1 & V2 positions. Get a good NOS matched pair, and there are still places to get good ones.
You can always try swapping the power supply cables to see (well hear) if the noise switches channels. Then at least you'll know whether it is in the power supply or the phono stage. The next thing to do is swap the tubes in right and left channel in the phono stage and/or power supply.
Oh heck, just go all out and get the second power supply. Swap out the EL-34's for some KT-66 and let 'er rip.
Enjoy!