If you sit bones are wide you won't get proper support from most saddles, which are designed for average width sit bones.
I had mine measured soon after I started road riding, and they were average (around 138 mm) so the saddle that came on the bike (a Bontrager Affinity RL) was great, and I got a carbon version of the same saddle when I upgraded the bike. Barely any padding, but still pretty comfortable for hours.
Edit: It helps that I've a well padded posterior!
Just had a friend get his sit bones measured (as he was suffering) and he is narrow (125 mm) so he's gone for a narrow 128 mm saddle.
If you are much wider than average, you will get the saddle pressing on your perineum, and shifting from one side to another won't help much, as you'll still get one side of the saddle pressing.
I know Bontrager and Specialized (and a few others) do a sale or return, where you can get your sit bones measured at a LBS, get an appropriately sized saddle and if you don't find it comfortable, take it back with in a month or two (so long as it is in good nick).
I would also pay attention to the profile the saddle is designed for. A lot of fancy saddles are aimed at young, flexible, riders who adopt quite an aggressive stance, shifting weight forward on the saddle, and also onto their arms. Being much older and less flexible, I sit more upright and move weight backwards on the saddle, and off my arms onto my arse! Therefore I went for a saddle (and padded bib shorts) designed for a relaxed posture (profile 3 as Bontrager call it).
Cheers,
Geoff