You'll use your round knife more than any other tool on your bench, so its cheaper in the long run to buy one really good one from a reputable tool maker (Gomph, Danny Marlin, Etc.) instead of two or three that don't fit your hand or won't hold an edge for long. I've had Tandy, Osbourne and Whatever brand they sell at Siegel of CA (the ones supposedly from England). The first one I could never get sharp, the second one wouldn't hold an edge and the third one the blade comes out of the handle so I know wherefrom I speak.
As for sharpening, all I use is a fine grit diamond hone and a rouge board.