Dual/multi ISP routing confusion

Hi folks. I've posted this problem on a (very much) older thread and it looks like it doesn't get much attention anymore.

I've got 2 ISPs and one LAN. Each one has one NIC. Now, I did manage to get an acceptable load balancing using nexthop but some web applications we use don't want to work with split traffic. So I've figured that I'll have to leave the ISP's mangling alone and route some hosts from the lan to one ISP and some to the other.

I just don't seem to have any success...
or
with appropriate route inside the lan host*
Still routes my host thru the default gateway.

I'm not even sure it's possible, anymore...
Can I make one computer from the lan go thru the router towards one ISP and another computer towards the other ISP?
iptablles, ip, route?
Ideas and guidence will be greatly appreciated. I'm expecting a third ISP to arrive shortly...
Cheers,
Alex.