I have been diving a Dolphin MCCR since the real old days. The total conversion cost less than $1000,00. I use my own no buzzer/alarm PO2 gauges. I use bird precision orifices. With planning, the conversion can cost very little. It depends on how you intend on diving it. Mine is designed for 100 msw, though I have only done it to 70. It is also designed to switch off-board gases on the fly
www.airheadsscuba.com/rbrsprt.html the links to my various pages is from there.
The dolphin is easy to breathe, easy to clean, easy to modify and it is operator friendly. It does have some idiosyncrasies, as they all do.
Dale