That's a nice receiver though it's funny now seeing all those s- video connections (which have obviously been replaced by HDMI). You can pretty much use any 'normal' speaker you find. And most 'normal' speakers are 8 ohm so...
If you wanted to move up to digital too you could add an OPPO blue ray which is a fist class blue ray, SACD, HDCD, etc etc etc player which also has multi channel audio out - but that is probably way beyond what you'd be looking for.