The X6 is a good phone (better than the N97 IMO) if you can live without the keyboard (and FM transmitter, compass, 32gb memory). It has over 300mb of free space on C.
E72 is a cracking phone if you can live with qwerty only and the lower res non-touch screen.
Vivaz is ok, faster than the X6 with a nice front end to symbian. Feels a tad cheap to me though.
Satio is high end but only if it's the camera that floats your boat. It's battery lets it down a bit. Similar front end to the vivaz.
Are those offerings based on the network replacing a symbian based with another symbian phone? If so they are all pretty much near the top of the symbian tree at the moment. It could also be the case that the N97 is no longer high end in the eyes of the network due to it being a year old now.
If you want to argue with them about the high end perhaps ask if they are willing to offer you an HTC Desire? It's high end (and one amazing phone) but generally around the same price as a satio.
One question, I assume that the replacement is for a 'contract' phone and not for a handset that you bought outright ? If it's a contract phone you have a tri partite agreement with CPW, The airtime provider(VF, 3, T-Mobile etc) and yourself, so you have someone else to involve and if you purchased the phone you should be able to get any phone you want of equivalent value or your money back. I'd push for the phone you want and don't be fobbed off !!
PS @Psychomania, you're such an Android Fanboy 
Hope you enjoy the desire!
I've had one for over a month now and it's still yet to lose that "wow factor".
You will be disappointed with the battery life initially but it does settle down after a few cycles and can be extended with the aid of certain apps.
You'll also get a free update to the new 2.2 "froyo" OS later this year which improves it's already great performance and adds plenty of extra features.
If you need help with it visit:
http://androidforums.com/htc-desire/
