Opinions on Bike I'm Considering

A buddy of mine is looking to sell his 2000 Kona Haole (one of his five immaculate bikes), and I think the price is pretty good.  More on that later.  Anyway... this is a picture of what the bike looks like, but this is a Kona image, and his bike looks much better with his upgrades.

The bike is a mixture of Shimano 105 (brakes are stock) and upgraded Ultegra components (derailleur, shifters, etc.).  The frame is a Easton SC7000 Scandium alloy (aluminum blend?), and the front fork is a carbon composite.  Upgrades include carbon fiber crank (I forgot the brand and model, but knowing him, it's high-end), Ultegra components (mentioned above), new wheels (bladed spoke Shimano WH-R561), Easton carbon fiber bullhorn bars with clip on aero bars.  There's also an upgraded seat, but I would replace that with a more comfortable model.   

I wasn't able to find an exact match for the handlebars online, but this one is pretty close.

Back in 2000, the bike retailed for $1799.  He's offering to sell it to me as is (with all upgrades) for $600, or $500 with standard handlebars.

The bike I'm riding now is an entry level 2005 Marin Venezia with Shimano Sora components and basic SPD pedals (which would be transferred to the Kona if I buy it... at least until I can get some SpeedPlay cleats and pedals).  It's an aluminum frame with a carbon front fork.  I've started noticing some clicking coming from around the bottom bracket, but nobody can seem to find the problem area.

Anyway... when I test rode his bike this morning, it felt extremely responsive.  The difference in weight is pretty substantial.  I'm guessing that mine weighs in at 23 lbs or so.  His (no water, cages, etc.) is around 17 lbs... or at least that's his best guess.  Lifting the two bikes was like lifting a bowling ball (mine) and a feather (his).

So knowing that all of his bikes are extremely well cared for and are ALWAYS tuned up to peak condition, I know that I'd be buying a bike that is going to work for many years.  I'm just curious what you think about the components, bars, etc., as well as the price.

Thanks in advance.  I appreciate it!

-Joel