I have worked in Medical imaging industry, If budget is not a constrain; I would recommend FAS6XXX series along with SAS disks, else FAS2XXX or FAS3XXX would be sufficient, but I strongly recommend SAS disks and as IOPS for SATA wouldn’t be sufficient serving your needs.
The new FAS22XX (newer hardware with enhanced performance) & FAS3xxx series should be sufficient for what you are trying to do. You have the choice of SAS, FC & SATA disk drives (SAS & FC have higher RPM). You may also leverage PAM cards for flash.
Flash Cache is a hardware option which improves I/O performance. You are specifically asking about how to maximize performance, therefore you might want Flash Cache. The FAS2240 series doesn't support Flash Cache therefore you should not purchase one of these if you want Flash Cache.
Edit: FAS2240 does support the new Flash Pool feature which is also designed to improve I/O performance so that may be acceptable for your requirements.