Those are some mighty pricey suggestions for a grado sonata :)
The aesthetics rhea is nice, but uses a multitude of tubes and making it behave quietly is a challenge to say the least - i was unimpressed. I have not heard the Steelhead, but retail is over $7k! Obviously Boulder will be ridiculously priced as well...
In any case, you do need to state your budget. I would think you'd want to stay under $2k for sure, but even then, your choices are many.
For around $300 used, the Lehmann Black Cube (especially with PWX power supply) is a good one. The Grado is also supposed to be decent but I haven't heard it.
A little further up the chain, for around $1200 a used ARC PH3SE will do nicely (it's the one I use with my dynavector 17d3) - dynamics, detail, nice warmth as well as rhythm and flow - it has it all. Even further up the chain is the JLTI (an excellent value, although it can sound a little mechanical, but may be good with the sonata) and then the Pass XONO, which will be under $2k as well (used). The XONO is a real performer, with everything you'd want from a reference phono stage (and also will hold up performance-wise even if you make serious cartridge/table upgrades).
Finally, if you're looking to spend the kind of cash that Mechans is advising, make sure to check out the Rossner and Sohn Canofer. It's around $7k as well I think, and is a reference quality phono (excel stereo in canada sells them http://excelstereo.com/Rossner/Phono.htm, as well as John at MyKindOfMusic.com)