For low end systems, I'd recommend:
-Playing with the Fastmode= setting in RR.INI (try: -1, 0, 1 and 2 to see)
-A Skin that does NOT use FLASH, and is the same size as your screen's resolution
-Disable transitions: transition=-1 in RR.INI
-Disable gestures: usegestures=false in RR.INI
-Use Winamp 2.95 -- remove any plugins from it that you do not use
-Do NOT use the GPS setting in RR itself, leave that only to Mapmonkey
There's no reason why RR should lag 2 secs to control volume -- even my Pentium 200 Mhz with 64Mb RAM and 4Gb HD running Win98SE has immediate effect over the volume.