Lots you say? I can't count them.
I made up a spreadsheet of all the legacy songs that are now on sale, and included a notation for all the ones that offer a Pro upgrade (information that I got from the Wikipedia page for Rock Band DLC). I've only got a few more of these to buy, so I just search for them by title now. But if you don't have a list already made? Yeah, it is a bit of a pain.
It looks like you can also pull up a list of all Pro Guitar songs using the Song Finder on this website. That makes it easy to filter the results by Source / Decade / Genre.
your lucky. it happens to me pretty much every time, and it happens to a lot of other people on PSN.
Well it's not like I spend hours in the store, I usually just know what to buy, and put them in background for speeding up things purpose.
Wow, I never got kicked even if I was browsing to find 20 specific songs through title. It wasn't long but still took a while to get them in background.
The week that Train and Eddie Money both got pro upgrades, it took me an hour and a half to buy them. And they were on the first page of everything. The store just kept kicking me relentlessly.