How would i do this - routing between VLANs

Hey guys, here's the idea:

I'm getting a Mitel phone system, VoIP, and so i need to have two VLANs set up - one for the phones, one for data.   i have two Dell 24 port POE switches, but need something to route between them.  There is a Cisco PIX 506E that i could get hold of, but wouldn't i need an ASA with a security license to route between VLANs?  That would save me from buying a router, right?

So what would be best?  Buy a layer3 switch?  Buy an ASA with the security license?  Or buy a router?

I'm open to ideas - want the cheapest method.