Hey!
First welcome to the AC.
It those were your dad's old system I wonder what is he using now.

Anyway, it was nice of him to pass on those to you. And I'm glade to know that you are not going to sell it.

As for the value I checked eBay and see that your SX-750 go for from $25 to $157 the second highest was $91. It is a good looking receiver. Look like it is rated as 50 watts per channel.
Your speaker is quite interesting. Are these the same one...

A little search and found this site...
http://www.thunders.ca/tangent/rs2.php Look like a very nice speaker for '70s and seem to have a good drivers there.

I've never seen this before.
As for the sound I'm sure the speaker and that old Pioneer sound very good and probably better than the new recent
iPod generation's system So, if you are taking them to your dorm too than be careful not to let your roommate break it

Just hook a CD player or an iPod up to it and I'm sure you will probably have the best sounding system there.
Take care,
Buddy