Well, Neo forum is a shit can of sorts. Asking for a Duo or NeoGeo CD for all the stuff he has may be a stretch, but I can easily see enough stuff there that he has to offer up as equaling the amount of a Coregrafx or modded TG and games.
Honestly though my advice to the OP is to take his stuff he doesn't want to ebay and ebay it if he cant get a fair trade here. After that he can buy a loose Coregrafx and hit up some sellers for loose hucard titles. Airmail with tracking will be cheap on those from import sellers, and there is plenty of good titles to be had on the hu-card side of things. The TG/PCE is easily one of the only systems out there where you could ignore the add on, in this case CD side of things and still be perfectly happy due to all the quality titles.
http://www.videogameden.com/hucard.htmOP can use said link as a guide of sorts to start off with on picking up some good hucard titles.
EDIT: Just a bit of advice to the OP. The odds are good that you may be assuming your stuff is worth more then it actually is. It helps to have a 3rd party with experience in sales with no interest in the matter get you price estimates.
Loose N64 stuff doesn't hold much value outside of the flagship titles like the Zelda games, Smash Bros, Mario Kart, etc. Genesis wise you have a lot of games, but only a few are true must haves that retain decent value when loose.
To complicate matters the fact is you might be willing to offer it all up in one lump sum for a Duo or Neo Cd, but it will be extremely hard to find anyone wanting it all in return. You may have a lot of stuff interested parties will already have or dont want, which may force you into doing a cash offer along with some of your games. You need to be prepared to do that if your heart is set on a Duo or Neo CD. I saw the Neo thread just now and yeah they are being a bit unfair. Honestly they should have just said what I did just now and left it at that.
Seriously, ebay is your friend in a situation like this. Split the stuff up, sell the games individually, save up the money you make and put it towards the item of your desire.