I think it would be better to invest in a better DAC than getting an OPA for the T1.
But then again, if you upgrade you can just swap the OPA in the new DAC with the upgraded one you have.
**edit:
I'm not too good with op amps, but isn't the OPA2134 the op amp people upgrade to from their current op amps? I know a modder that swaps out the stock PSX OPA with the OPA2134 and new power supply for it. So I guess its already pretty good.
But then again, if you upgrade you can just swap the OPA in the new DAC with the upgraded one you have.
**edit:
I'm not too good with op amps, but isn't the OPA2134 the op amp people upgrade to from their current op amps? I know a modder that swaps out the stock PSX OPA with the OPA2134 and new power supply for it. So I guess its already pretty good.