Hard to say. I have a 2004 Raleigh Supercourse fitted with mostly 105 and have been having a blast on it lately. It has just under 815 actual miles on it even though I'm the original owner (bought it on clearance on ebay for $650 shipped back when the 2005 models came out).
I don't know what the bike is worth today, but Raleighs from that era don't hold their value at all. All I had to do to get the bike to "fit" was buy a 30 degree 80mm stem and now it's one of my favorite bikes to ride, whereas before it had sat in the garage for over a decade because I felt like I had to reach too far out to ride it.
I guess my point is, I'm not sure spending scads and scads of money would guarantee that I have "more" fun or get "better" exercise than that '04 Supercourse. Some new tires might help, but that was a time when 700x23 tires were the de-facto standard road tire. 700x25 BARELY fits the front fork. 700x26 does not fit.