Good day,
Hi, You need minimum sup-bootdisk:s3223-advipservicesk9_wan-mz.122-18.SXF7.bin IOS to enable INLINE mode on 6500 series.
as per my knowledge,
the latest IOS is
sup-bootdisk:s3223-adventerprisek9_wan-mz.122-18.SXF13.bin.
for IDSM-2, if u upgrade to Engine 2 IOS, U can get update with E2 signatures and also U can manage from New Management Console like Cisco IPS manager Express 6.1.
I hope this will satisfy.