I'd looked at one of the 5 gallon models once while on sale for a mash tun. I'm pretty sure the pouring spout will keep you from using this as a carbonating vessel. I doubt very seriously it will hold up to the pressure.
What are you using for a "fermentation vessel"? Can it be completely sealed? Most things you'd use for fermentation have an escape value by design since you don't want to trap the CO2 during fermentation...only later.
To take beer from a carbonated container to another serving vessel you'd really want to keep it under pressure the whole time. This is the kind of thing you'd do if you carbonated in a keg and then needed to send bottles to competition. You'd need to use a counterflow filler to make sure you 1) didn't oxidize during the transfer and 2) maintain the carbonation. Of course, this is all moot is you plan on drinking it all at one go! Taking it from carbonated keg to a portable serving vessel is like getting a 5 gallon growler at your local brewpub (hmmmm...I like that idea!!) The idea though is that it will be consumed immediately so losing carbonation and potential off-flavors from oxidation aren't important.
If you're looking for a cheaper start at kegging I'd look at maybe going with the 5L mini-kegs (the kind Warsteiner, Kulmbacher and others are using). You can buy the products, drink the original beer and then just reuse the cans. You can also buy the mini-kegs and systems online ...
http://www.beer-wine.com/product_info.a ... ectionID=1 ... is one example.
I've never used them but B3 has a Tap-a-Draft system that looks interesting ...
http://morebeer.com/product.html?product_id=18291 ... I'm sure you can find a homebrew shop in Canada that would carry one of these systems.
David
