I replied to this in your other post...but I will paste that reply here as well.
I am not sure if there is a tool for migrating the configuration from PIX to ASA8.3+ If there is, I have not come across it before. I do know that if you are upgrading from 8.2 to a later version the ASA will migrate the commands itself...though I have had mixed results with this as there have been many duplicate entries.
I did come across this webpage that has a tool for migrating NAT rules...which might be useful. I just did a couple small tests with it and it seems to work fine...though I am unsure how it will handle a large amount of rules.
I agree that I am not aware of a tool to migrate from PIX to ASA5500X series which runs 9.x code. And my experience with the tool that did migration from PIX to ASA pre 8.3 code was that it did not work well for me. I pretty much wound up doing the migration manually.
The other part of the question was about whether to choose ASA5525X or ASA5545X vs ASA5550. My advice would be to choose one of the 5500X series. They will have more processing power than the equivalent ASA5500 model and they will support more features. Also the ASA5500X will run newer code (the ASA5550 is not supported in code past 9.1). I would have pointed out the issue of End of Life announcements for the ASA5550, but for someone who is still running PIX I guess that is not much of a concern.
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
Table of Contents Introduction:This document describes details on how
NAT-T works. Background: ESP encrypts all critical information,
encapsulating the entire inner TCP/UDP datagram within an ESP header.
ESP is an IP protocol in the same sense that TCP an...