Overhead with Hyper-V

Hi,

  I am working on new server project and trying to determine if I should go with Enterprise SATA HDs 7200rpm or SAS 15K HDs. Here is why I am in a quandry.
  A year ago I installed a new server w/ 32GB and 2 x 2TB Enterprise SATA HDs doing RAID 1. I setup W2012 to run Hyper-V (200GB HD space and 2GB RAM). On the top of that, I created three VMs: (1) SBS2011 with 16GB RAM, 200GB OS partition, 800GB Data partition)  (2) Windows 2008 R2 Terminal Server with 6GB RAM, 200GB HD  (3) Another Windows 2008 for Quickbooks Database server with 4GB RAM, 100GB HD

  Whenever I connect to this server whether I am connecting to Hyper-V or any of the VMs, I just feel that the respond is much slower than my (1) 5 years old "Dedicated" Windwos 2003 SBS Server with 4GB RAM, LSI HW  RAID Controller w/  Enterprise 7200rpm 1TB HD x 2 (RAID 1).  or (2) 2 years old VMWare box that has 10 VMs w/ 32GB RAM and six 600GB SAS 15K on RAID 10.

  Having said that, is slowness that I am experiencing normal given the fact that it has Hyper-V with VMs on 7200rpm HDs? too much overhead?

  So I wonder if I should just setup this new server, w/o HyperV, as "Dedicated" SBS2011 only with 16GB RAM and setup another server box with HyperV to run a couple of VMs such as Terminal Server or what not. I was trying to save a few dollars by running EVERYTHING (OS + VMs) on an economical 7200RPM SATA HDs. As long as it has lots of RAM, I thought it would be ok.