Optimal CPU temps?

I have an Abit BH7 & P4 2.4B, It is oclocked @ 3.55 / 1.65 Volt and I have watercooling installed. The thing is that I have my GPU on watercooling too and the temps I get from the BH7 are 46 C idle (CPU) and 50-52 with Prim95 . In the begining I thought it was a BH7 prob , misreading temps but when I touch the system (Nortbridge) chip it feels like as the bh7 reports (33 C idle , 40 C with Prime95) . 37 C is the point where you can tell the diference because thats the temp the human body has, below you feel the chip is normaql to cool and above you start feeling the heat, over 40 it feels very hot and if you cant touch it then you are at 50-60C. My question is: Are my temps good? Consider the Oc (2.4 running at 3.55 ! stable with 1.65 Volts). Consider that I have my Geforce 4 Ti 4200 on the same watercooling and it is oc too from 225 GPU to 306 . That puts extreme heat on the watercooling system. I live in Greece so ambient temps especially now in summer are high , lets say 27-30 and they get really higher (35 C) in my room which doesnt have a good ventilation....
Also , the northbridge chip gets hot, it had only a passive heatsink and the temps would climb to 50C , now that I put a small fan on it (loud too) its droped to 40 (these temps are running Prime 95 for several hours).
Also I dont use arctic silver but arctic alumina, or something similar, If i buy arctic silver will it have an impact on temps?

??Any thoughts?

What type of watercooling setup do you have?

Block, pump, radiator?

Its handmade, I have a swifteck mc5000 cpu block, a mc50 gpu block , a pump (unknown brand and specs, although medium in power) and a radiator from a motorcycle.

considering the load on the system, your temps don't look too bad IMO. With the swiftech stuff don't they use 3/8 tubing aswell? medium power pump doesn't say alot to me. But if you want lower temps maybe use a more powerful pump, i'm from the uk so i think eheims are the only easily available in europe. And bigger tubing 1/2". How big is the motorcycle Rad? car heater core could be a cheap upgrade.
Just my thoughts.
later