Set Windows pagefile size in answer file

The traditional answer would be to separate the pagefile from the System drive but the X-25E's performance should generally make that unnecessary, especially on a server. If you can't put enough RAM in the system to avoid unnecessary paging, or you have applications (like Exchange 2007) that can make quite a lot of use of paging no matter what, then putting the page file on dedicated disks or on disks where the utilization is generally low remains a good idea.

However using a single X-25E for the system drive seems a bit strange to me. Whether it is a good idea or not to use SSD's for the system drive depends entirely on what you are using the server for but in most cases system drives on (properly configured) servers are not going to be the most significant IO bottleneck you want to control.

What I can say for certain though is that you should not use just one drive for system or normal data volumes. The standard practice of using two relatively small but reasonably fast drives (2x10K SAS) in RAID 1 provides sufficient performance to load the (mostly static) system drive files for most servers but guarantees you some level of failure resilience. SSD's might not be mechanical but they can, and do, still fail.

Ideally you want to use SSD's to eliminate something that is IOPS limited - your RAID 10 arrays are probably able to get close enough to matching the X-25E's transfer rate under most conditions but they wont come close to the IOPS (a couple of hundred at best versus many thousands for the X-25E). However since it's a single drive you should be very reluctant to put anything that you can't afford to lose completely on it - if it was me I'd be using it for temp file space (print spooling for example, scratch DB area for reporting etc).

The 1.5 times physical RAM is just a guideline. There are some general pointers about page file sizing in this Technet article which makes the point:

On server systems, a common objective is to have enough RAM so that there is never a shortage and the pagefile is essentially, not used. On these systems, having a really large pagefile may serve no useful purpose.

However for some systems (Domain Controllers, Exchange Servers) totally disabling page files is not a good idea. It's specifically contra-indicated for DC's and it's a very bad idea for Exchange Servers. I've seen the Exchange behaviour described in that article (extreme disk thrashing caused by paging) on an E2K7 Server that wasn't all that busy with 32G of physical RAM where someone set the pagefile size to 1G.

I've never found (or heard of) any specific statements that indicate a paging file is necessary for SQL, apart from the general argument that it helps if something else goes rogue and chews up all physical RAM.