If you are looking to change, consider the Scubapro MK 25 with the S600.
I must agree with you on the suggestion of regulators. I own the MK25 S600 and 600T and they are performers. I use the MK25 S600 on my bailout. The 600T was my primary for open circuit diving, until one day a friend stuck his
Atomic B2 regulator in my face and I took one breath, removed the reg, looked at it, and then drew another breath.. OMG, performance was WOW.
In fact I liked them so much I bought 8 of them.

If you can find an MK25/600 and an Atomic B2, try them both and compare for yourself. They are both excellent regulators, but I've got to sway towards the B2.

Good luck on your selection.