Hi Bro
Just to understand your question once again, you don't have anymore available slots in your present Cat6K, but you want to know how to secure your VLANs or SVIs that has been configured in your Cat6K?
If you were to ask me, I would not apply a bunch of ACLs in the Cat6K, for starters. You might wanna look into COPP (Control Plane Policing) instead. Furthermore you could also refer to this Cisco document http://www.cisco.com/en/US/products/hw/switches/ps708/products_white_paper09186a00801b49a4.shtml
However, if you do have Cisco ASA FW appliance (not module, I presume from your question), you could enable ACLs, threat-detection feature, IP Audit features, reverse-path policing, capping of the embryonic values etc.
P/S: If you think this comment is useful, please do rate them nicely :-)
Warm regards,
Ramraj Sivagnanam Sivajanam