1970s Kustom 150-1

Hi guys!

I have a late 60s early 70s Kustom 150-1 guitar amp.  I would like to sell it so that I can get a JB Epi model.  What woudl be a reasonble price to ask?  Is $500 to much or too little?  Does anyone want to buy it or trade for a JB Les Paul? 

Thank you!  I NEED to get a JB Les Paul!!