Buying that amp isnt the best idea,the thing is that the seller most likely knows full well whats wrong with the amp & is aware of repair costs,imagine if the amp was yours,wouldnt you get a repair estimate before dumping it?
Dont ever believe what you read on ebay,in my experience sellers with experience who list amps as being untested,cords cut off,tubes missing ect are liars,they count on people's greed & wanting to score a sweet deal,this guy's feedback shows a pattern of denial,inaccurate desrciptions & hard to contact when auctions go bad,are you sure you want to deal with this guy?
The reserve price alone is nut's,did you read that his reserve is $199.00 for a broken amplifier

,i could see if this amp was rare of worth fixing but at his reserve price plus the cost of repairs you could easily get a brand new amp from Crown,Alesis,Behringer ect.
With your budget of $300 it will be easy enough to find a great amp,look on
http://www.audiogon.com/ using the zip code search function,keep looking on ebay using the nearest first feature & if they both fail go to your local guitar center & buy a new amp.