Are any speakers suitable?

A friend of mine wants to buy new speakers for an old receiver (Kenwood KA-A5060); the manual can be found here [kenwoodusa.com]. Is there anything special to consider when looking for replacement speakers?

As you can see the receiver is old (the manual makes note of where to hook up your turntable ) - an alternative for him is a new HTIB (I am personally a fan of Onkyo's outlet/refurb center); how cost-competitive will this be vs new speakers?

You need to consider the impedance and watt rating of the speakers. This system has the ability to be adjusted for a pretty wide range of impedances (page 9), but with some settings only two speakers can be attached to the receiver. Information on wattage can be found in the specs on the last couple pages. It's desirable to buy speakers rated for a higher wattage than what the system can output. 8Ω speakers would be the safest bet.

With some planning, new speakers would work with a new receiver should it get replaced at some point and the speakers would probably be higher quality than the HTIB ones. This receiver doesn't even support Dolby Pro Logic.

According to the "Connection of speakers" section, if you want to use two sets of speakers at the same time you will need to stick to impedances between 8 and 16 ohms. Otherwise, 4-6 ohms are also OK. Be sure to set the impedance switch appropriately, while the unit is turned off.

Also the model number in the document (KR-A5060) is not quite the same as the one you give, but I have no idea if that matters.

Will this be for music or his TV?
Regardless of which it is, Asian made speakers will be irritating and American (or Canadian and/or European) speakers will give him more musical pleasure than ever, unless he already had US made speakers.
If it's for a TV application, it becomes a bit more difficult, as one would want some big deep bass, which could get expensive with US speakers.
As mentioned above, you'd try to get 8 ohm speakers, but if necessary, 4 ohm will do.
There are tons of brands of good speakers, and if your friend is truly interested, I can give you a short list.

probably both TV and music however I am sure he is interested in surround sound for BR, etc (which leans toward a new system altogether).

I wouldn't worry too much about impedance. Most speakers are 8. What I would worry about is that units ability to burn out tweeters. That will reach full volume at around 10 o'clock on the dial. Any more is just distortion and will melt the tweeter in a hurry. I'd say dump it and get something modern.

I all of a sudden feel real old.

Quote from Lavin : I all of a sudden feel real old.

I was around when they built the Walls of Jericho.