SECURITY QUESTION ABOUT WEBSERVER, IPS, AND CISCO ASA FIREWALL

Hi, we're about to add another web server in a DMZ to our network. How do you recommend doing so? Here is our current setup: We have a Cisco ASA 5505 Firewall and a Linksys RVS4000 IPS Router setup in the following manner:

INTERNET >> Cisco Edge Router >> ASA Firewall >> Linksys IPS >> Network

How do you recommend doing the network now that we're adding a web server? Here are 3 ideas I have:

IDEA NUMBER 1:
                                                           Webserver
                                                                    ^
                                                           Linksys IPS
                                                                    ^(DMZ)
INTERNET >> Cisco Edge Router >> ASA Firewall >> Linksys IPS >> Network


IDEA NUMBER 2:
                                                                                   Webserver
                                                                                            ^(DMZ)
INTERNET >> Cisco Edge Router >> Linksys IPS >> ASA Firewall >> Network


IDEA NUMBER 3:
                                                                                    Webserver
                                                                                            ^
INTERNET >> Cisco Edge Router >> ASA Firewall >> Linksys IPS >> Microsoft ISA Server 2006 >> Network

Do any of these setups look good? I like Idea 1 personally because we don't have to buy another server, just another IPS box (~$110 USD), but I'm concerned about the internal network's security because the DMZ and LAN are on the same box (even though all traffic from the DMZ to the LAN is restricted). Idea 2 I'm a little worried about because the Linksys RVS4000 IPS router isn't behind the ASA (which undoubtedly has a much stronger firewall and is much more secure because it runs Cisco IOS) and because of the same reasons as Idea 1. Idea 3 would be more expensive than either of the other 2 ideas but, if I'm not mistaken, is more secure than the other ideas. Is this the case? Are my assumptions accurate?

I already have a copy of ISA Server 2006 to install on a new server. Cost is not an issue; security is.

Is the DMZ on the Cisco ASA as good as having a secondary firewall (ISA Server)? The ASA has all traffic from the DMZ to the inside network restricted (cannot go through). If possible, I'd like to go without buying another server, but if we have to, I will.