Hi Glenr,
Regarding you quest for 5.25" to 3.5" HDD bay converters you can always go for models that turn 2 No. 5.25" bays into 3 No. 3.5" bays like those offered by Lian Li, see
http://www.pccasegear.com/prod5981.htm
Lian Li, Silverstone and coolermaster also offer similar models that turn 3 bays into 4 etc. may be a way of squeezing more bays into your existing server case.
All have fans to cool the disks.
Craig.