I'm not sure how different the SWR WM4004 is, but I've played a WM8008 a couple of times recently (with an SWR 810 cab) and thought it sounded like crap. I won't say that all SWR sounds bad - I heard some fantastic sounds coming from a guy with a SWR Redhead and a Hartke 210.
I haven't tried any of the Fender bass amp, so I'll decline to judge.
I've found the Ampeg SS amps to sound sterile. Ashdown and GK sound better to my ears.
My preference is for all-tube (I'm lovin' my SVT-CL), so my opinions might not mean squat for what sound you're wanting.