I am vetting the purchase of the RME fireface 800 vs. some other audio interfaces.

I have a toshiba laptop
Model = A505D S6008
8gb of ram,
AMD turion II Ultra dual core mobile M620 (each processor = 2.5gHz),
a glyph 1tb 7200rpm External Hard Drive (connected via an built in eSata port),
running Windows 7 (64-bit), 
Pro Tools 9. 

The toshiba laptop does NOT have a 'built-in' firewire port.  I do have an 34 express card slot.

I am thinking of purchasing the FireFace 800 and a Sonnet 2-port FireWire 800 Pro ExpressCard (Texas Instruments Chipset), perhaps the RAIN ExpressCard.  Both appear to be highly rated.   
*** I am unable to locate a single-port fire wire 800 express card adapter. 
*** I INTEND on ONLY making use of 1 of these ports.

MY SIMPLE QUESTION:
Will the fireface 800 work with this setup and will it work at the 800 transfer rates (NOTE: using Windows 7, 64-bit)?

Now I've seen links provided that instruct users experiencing firewire connectivity problems to switch to legacy 1394 drivers when using Windows 7. 

HENCE, MY SOMEWHAT MORE COMPLEX QUESTIONS:
1) Will using the legacy driver (1394a = fw 400 = 400 mbps) result in Latency issues or drop outs?
2) Will FireFace 800 run optimally when connected @ 400mbps transfer rate, meaning will I be running a BENTLEY on REGULAR GASOLINE ?
3) Would the FireFace 400 be more suitable, although NOT AS WELL RATED as the 800?

I currently use a Lexicon Lambda: I know, I know -- Guitar Center recommended it for my ostensibly basic needs.  However, the drivers are terribly poor and there a/d d/a converters are probably inferior as well.  LATENCY when recording audio with pre-recorded audio tracks playing back is REALLY AN INSURMOUNTABLE issue to work around, and renders the device AUDIO impotent!  Nevermind trying to record jamming sessions with multiple audio inputs, which is, btw, my most important need. 

So, what is a po boy to do?  Must I resign to purchasing an Apple Mac Book Pro.  I can't stand jumping on that  bandwagon: nor do I want to.

Are there any definitive answers at all.

I am not made of money RME ($1700), MacBook Pro (+$1000), Pro Tools 9 (nearly $600).  You would think with all the upgrades and 'new and improved hardware', programmers and manufacturers would come up with a DEFINITIVE LIST of WHAT WORKS WITH WHAT.  Oh, that may be an oxymoron.

Praise be onto WhOMeVer comes up with an eSATA connectable AUDIO INTERFACE.  External Hard Drives come with all flavors (eSata, firewire 400, 800, usb 2.0) ... for what are audio manufacturers waiting?  Just scan through the forums on any and all of the myriad Audio Manufacturer's websites and see all the PC users with all the infinite issues.  Oh, the issues never end.  There's your marketing to justify building a SOLID 'MADE FOR PC' Audio Interface.  Well, we all know there will never be such a magic bullet.  So many computer manufactures, so many operating systems, so many hardware and software configurations -- permutations upon permutations.  And I am a programmer by trade.  Just writing this is giving me a headache.

Would really appreciate some solid insight and suggestions, definitive or not.

Thanks in advance.
Gary