Upgrade from Fubar II

I currently have a Fubar II with OPA627s in place of the stock op-amps that I'm using with a Little Dot Mk V amp and DT 990s. I love the setup, but I have a feeling that I could be getting more out of it. I definitely want to stick with the Little Dot, but I'd like to know what else is out there in terms of DACs that might fit my amp/headphones better. If there are any good tube DACs out there I'd be interested in those too, but either way, I'd like to spend less than $200. Is this possible?

Thanks

Any ideas? 

Interesting, I thought it was pretty widely accepted that the OPA627/637 were the best in terms of opamp quality. Is the 602B new? Because I haven't heard of that one, but I'd certainly be willing to try something else. Also, does the Supplier really make that much of a difference? I figured that since it wasn't driving anything with a high load that it really wouldn't need a beefier power supply. Thanks

Awesome, I think I'll try that out then. What sort of improvements would I see in upgrading the power supply?