They are not pin to pin compatible, the OPA2604 (not Chinese but made by Burr Brown not owned by Texas Inst.) is a dual (2 op-amp in the IC) and the OPA627 is a single.
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Edge, you can use the OPA627AP but you'll need an adapter board that lets you mount two single opamps into a double socket. This is usually known as a "Browndog adapter" but there are generic versions out there, too.
I have a Music Hall Mambo integrated amp (made by Shanling) and have been playing around with this opamp thing recently. There are two kinds of adapters that will work. One lets you mount both singles to the top of the card and you can get this with sockets so you can swap out the single DIP chips. This is convenient but make sure you have enough space around the original socket for this "double-wide" board to fit.
You can also get an adapter board that mounts one SOIC opamp on top and another on bottom. This requires you solder the opamps to the board but is very compact so it should take up not much more space than the original double DIP opamp. You can find pre-mounted opamp/adapters out there but they are pricy.
A Google search for "browndog opa627" should turn up your sources. TI's Asia-based production has OPA627's back in good supply. I ordered some last week and am anxious to hear what they can do.
I started by swapping the OPA2604's out for some AD823's (AD's cheap but similarly-spec'd double chip) just to see if I could hear the difference. I waited about two weeks to allow for any burn-in before I made any judgment. After two weeks in my system, the AD823's were pretty harsh and forward, a definite difference not for the better. The OPA2604 sounds natural in the mids and highs (which I really like) but has weak bass and lacks some detail. So I decided to go back to Burr-Brown and move up the ladder.