Touring - Cannondale T800 .. tire replacement

The tires on my wifes Cannondale T800 need to be replaced. The tires are ContiTop Touring 2000 with markings (37 - 622) 28 x 1 3/8 x 1 5/8. I understand these to be 700 x 37 tires. The tread is worn off on these tires after 3 years and about 4000 miles.

The bike is ridden almost exclusively on pavement or hard pack roads.

Can these tires be replaced with a thinner tire say 700 x 32? I am also wondering if it would be better to replace the tires with something like Bontrager which has no tread, to lessen the rolling resistance. I have bontrager on my trek 520 and they seem to have performed very well, after about 6000 miles other then nicks the tires show little wear.

Thanks in advance for your opinions.

I can recommend Vittorio Randoneurs, I have their 700x28s on my touring bike. I really, really love these tyres, I did some decent off-road (with a 40kg load), as well as flying through unavoidable broken glass many times, no punctures in about 1500km so far. See link to 2008 tour pics in my sig to see the off-road trails I was on.

http://www.buzzillions.com/dz_168697_vittoria_randonneur_reviews

I think it would be perfectly alright to put on 700 x 32 tires. You can even use your current tubes.
Bontrager is a very good name in bike components. I imagine their treadless tires should make pedaling easier. Apparently bicycle tires don't really need treads because they end up just cutting through water, puddles, etc. (No hydro-planing) I read that a while ago in an article written by bicycle god Sheldon Brown.

A couple of thoughts. The T800 has a stiff frame and can transmit some road harshness when unloaded (I have a T2000). The Conti 700 x 37 is a fat and soft enough tire to absorb some of that for you if you ride without a load much of the time. Really nice tires imho, and they are also available from Wheel and Sprocket for $14.99 right now (I bought some). On the other hand I also love the Vittoria Randonneurs in the 700 x 32 size and they would certainly make the bike a bit faster.

Vittoria Randonneur 700x28 on a T800. A little harsh for me. A bit faster than the Michelin 37mm the bike came with, and much more puncture resistant.

I'm going up to 32mm next time I have to replace a tyre (which will be years by the look of them at this stage...)

Just to compare, 23-25mm tyres are fine on my steel fixie and on a Salsa casseroll I test rode, but no way I'd go any narrower on the T800 (besides which, 28mm is the thinnest the rims are rated for).