new poster, have questions adding laser to cnc router

Hi all. New to the forum. I have a small home based business with my DIY 4x8 cnc router. I cut quite a bit of sheet aluminum and am looking to expand my services with a laser. I am interested in either adding a laser to the cnc in order to engrave aluminum/steel if possible, or engraving wood/acrylic/glass. I would like to attach it to the z axis and I am planning on using water cooling(as I am currently using for my spindle). I have done a bit of research but in honesty, I have a lot to learn. I'm not going to jump right in and start messing with lasers as I realise they can be dangerous. I'm just looking for advise on my options so I can plan for the cost and learn the necessary info for whatever direction I choose. I have marked a few diodes from ebay as a staring point. I was hoping to get some general feeback on these diodes and if they would be suitable for what I would like to accomplish and if so, what other goodies I would need to make it work. Thanks. Kevin

808nm 15W High Power C Mount Laser Diode | eBay

http://www.ebay.com/itm/261267374706?_trksid=p2055119.m1438.l2649&ssPageName=STRK:MEBIDX:IT

Laser Diode 8 Watt 915nm Fiber Coupled 100UM JDSU 6397 L3 8W New 63 00332 | eBay

808nm 7 5W High Heat Load Laser Diode | eBay

Htoe Fiber Coupled High Power Laser Diode 8 Watt 810nm | eBay

I think I'm leaning toward the first or second one. Would either work for engraving wood/plastic?