There is no such thing as expensive if you want nice solutions for your loving machines.
The fact that IDE exists for example on A4000 doesn't compare with the awesome speedup and less CPU usage by using SCSI interface.
As mousehouse said, SCSI is awesome but it's noisy and also power hungry. For putting cheap and 2.5" HDs ACards are an awesome solution that work just fine.
Btw SysInfo gives a bit less results but I always known that SysSpeed was more trustworthy than SysInfo when it comes to drive reading numbers.
For example in my setup...SysInfo gives about 15.7MB/s while SysSpeed gives about 18.3MB/s. Still a great deal of difference comparing to the internal IDE @ 2.5MB/s don't you think?