I think it's not a question if PIX can do this, cause I don't see any reason why it shouldn't. Only thing to remember is that if you wan't to dynamically route traffic to two providers is that you will have to run BGP your own, and then redistribute this via OSPF to your PIX.
Or is your question more about having multiple static commands to the same inside IP adres (various outside adrsses due to the different providers)? There have been some postings about this, and this is possible, cause PIX will Proxy ARP for both static translated adresses by default.
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...
[toc:faq]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 and UDP are I...