I ran the benchmarks awhile back when I first got my SupaCelly. The default one came in at 1844.
C533A@825
Savage4 32MB
128MB RAM (at least)
So yeah, the S4 is maxed out. It is at least 1 1/4 years old and an S3 guy said it was a year late at that so it shouldn't be a surprise. Still, there hasn't been anything compelling enough when considering price and performance (including features and visual quality) to replace it with. I almost went for the S2000 but the GF2 MX is looking like a real contender if it can be had for less than $100 this month (post coupons and rebates).
That will be an incentive to rig some better cooling for the Celly too so I can run it all the time at the 897 I know it will do
You should make sure you have the latest reference drivers from S3 since they can make a significant difference. I overclock mine for an E-Z 10% increase using S3 Tweak or PowerStrip too.