My Teac HA501 really shines with all the Grados I tried (RS1, PS500, SR225i,
SR60i, SR60e and GR10. The Grado RA1 has very good synergy with Grado phones and is reasonably priced. My Woo WA3 OTL mates great with my high impedance phones (DT880 600 ohm , AKG K340 and 240 Sextett).
but is not a good match with the Grados mentioned above.