Agreed Valuation - opinions please.

I'm currently in the process of shopping around for insurance as mine is due to lapse soon. I've had a few quotes from companies that will offer agreed value for the car, what figure should I be looking for? I appreciate this is a very subjective question and it boils down to the usual points;

a) What's it worth to someone who wants it?

b) How much would it cost to replace it with a similar specification?

c) Falling market, you never get as much back as you put in, doom & gloom etc.

I've looked at the usual trading sites as well as recent classifieds on here for an indication. I have a figure in mind that I think is a sensible suggestion to any potential underwriter, just thought it may be a good idea to get any opinions on here from any knowledgable members.

The car in question started out life as a 1996 Facelift 6 speed with V161 gearbox SZ-R (I think) - I anticipate any underwriter will lower the valuation because it was "only an NA".

The additional specification is as follows:

Engine transplant with engine from an RZ having covered approximately 50,000 miles (genuine),

PHR Street Kit,

Tial Wastegate,

Custom screamer pipe,

3" Double De-cat (UK spec),

Veilside Titanium Teardrop Exhaust,

Greddy LS FMIC,

850cc injectors,

Mocal 16 row oil cooler,

Aeromotive Fuel Pressure regulator,

Emanage Ultimate mapped to approx 1.4 bar,

VEMS dual AFR/EGT gauge,

SPA design dual oil pressure/oil temperature gauge,

AEM Tru Boost controller,

RLTC with digi adjuster,

Southbend clutch,

HID headlights,

Larger OEM brakes,

Leather OEM seats,

18" Volk Racing Evo IV rims,

Yellow Bilsteins,

Pro sport mats.

Body is totally standard with immaculate paint work in gunmetal. Interior is pretty much standard and spotless with the extra gauges installed into the dash to look OEM. Here are a few (poor) pictures for you to appreciate the awesomeness.

Any suggestions on the agreed valuation target figure are most welcome...

http://img522.imageshack.us/img522/5378/0907071139.jpg

http://img522.imageshack.us/img522/8366/09070711391.jpg

http://img142.imageshack.us/img142/5416/09070711392.jpg

http://img142.imageshack.us/img142/937/09070711393.jpg