Mixing 1.5 and 3.0 Gbs SATA HDDs in RAID5 array?

[Bodine]

I have three 250GB Maxtor 1.5Gbps drives in a RAID5 array. I need to add a 4th drive for a hot-spare and there's a pretty good deal on a 3.0Gbps drive. Would there be any issues if the 3.0Gbps drive were to join the 1.5Gbps array?

I emailed Highpoint, the vendor of the RAID controller (RocketRAID 2310), but I doubt they'll get back to me until after Christmas and I'm hoping to order a drive today.

Is there a general rule of thumb for this, or is it controller-dependent or what?

TIA.