Paul,
Had I seen the supplies that CJACK sent the link to a few years ago when I did mine , I would have done one of those instead of the computer supply as it needed some modifications.
This one looks nice
http://www.ebay.com/itm/10A-30...c:g:nVYAAOSwqBJXUIWJ
It will provide up to 30 volts of dc voltage with 10 amps of current. both the dc voltage and the current limit are adjustable. If you think of the DC voltage adjustment like the handle on the Z4000, you can set it to your desired 8-11 volts. Given you indicate you are drawing 4-5 amps per side, I think the 10 am supply would work just fine, I think it is about $65 with free freight. Plus this is a complete unit, plug it into the wall, and connect to the GND and + (Green and Red) terminals posts on the front to your lighting wires. You have a fine and coarse voltage adjustment to get the voltage (brightness) you want.
If you would have double the capacity if you got 2, and for about $130 you can't touch a single Z4000 even used. The technology of regulated DC supplies have really developed in the last 10 years, offering great cost vs power benefit. They typically are very reliable.
After looking at these supplies, IMO it would be foolish to mess around with old toy train transformers, and even though I like the Z4000 and it is a great transformer, overkill for this type of job.
Just my 2 cents.
