Cisco Infrastructure :: ASA 3750 Firewall To Control Traffic Between VLANs

We have a data center with servers set up for different projects, some servers from partner companies and several small LANs. The traffic between all those needs to be controlled and firewalled. The servers and LANs are divided into different subnets and VLANs. Physically, their traffic is aggregated on a couple of 4506 and then sent to a FreeBSD server, where the logical gateways are set up and traffic is filtered between them.The BSD server is dying and having it there is incorrect in the first place, so we are planning to replace it with two ASA (5520) in failover.The question that arises is how to correctly implement firewalling between VLANs. Originally we thought to set up the firewalls in transparent mode and logically terminate VLANs on a stack of 3750 switches behind them, but would that filter the traffic between the VLANs? Then we thought to perhaps terminate the VLANs on the ASAs, use routing mode, and do filtering there, as well. Or should we implement multiple contexts? We have about 20 VLANs and all of them differ in rules of what should go there. None of this can be concidered an "inside" - trusted - zone, nor "outside". Internet and external links are connected and filtered in a different place.