The main "fleshing out" effect of a valve amp happens simply because of the higher output impedance, which has a noticeable effect on the frequency response. While this can be very pleasant with the right speakers, another way to go is simply to choose a pair of speakers with the response you require. If you want a 'fleshed out' response (by which I assume you mean something that dosen't suffer the usual brightness or the usual lower-mid thinness caused by the floor bounce) why not go for something like Harbeths or the old model Spendors - natural, honest, 'fleshed out' sound by design, not accident.