SMART Hard Drive Temperatures

I've always been concerned about the temperatures being reported by
SMART monitoring utilities I've used. I even ended up taking the side
of my case off and sticking some massive fans to the side to blow air
on the hard drives. This allowed me to put the PSU outside of the
case, too, as it was half an inch away from the CPU fan.

I recently decided to remove the large fans I'd added, because the
whole system was making one hell of a racket!

So, having put the PSU back in, and removing the extra fans, the CPU
now runs about 10 degrees cooler, and the hard drives about 20 degrees
hotter.

Now I'm getting temperature readings of 47-50 degrees C for the
primary hard drive, and about 40 C for the secondary hard drive. This
seems way too hot, especially when the CPU is at 45 C most of the
time!

I have read that the SMART temperature is usually taken from the
controller chip, which is the hottest part of the hard drive, and also
that the maximum operating temperature on the spec. sheet is probably
referring the ambient temperature (ie, not the temperature of the
drive itself.)

Should I be worried? The hard drives feel fairly warm, but not
scorchingly hot...