I run my K27 using track power, and have gotten the itch to put in sound. Don't have time/patience/skill for a complicated install, just want decent sound that I can drop in the tender. Anyone got some good advice? Also, I'd really like a whistle but got no idea how that fits in with the stated constraints. Thanks in advance.
Probably the simplest and cheapest solution that meets your criteria is Small Scale Railway. You can check them out at this site http://www.smallscalerailway.com. I don't see a specific sound scheme for a K-27, but you can listen to the 20+ they have an find the one you like best. Get the optical sensor on the 12 inch ribbon cable and you can do the whole install in the tender.
There are more sophisticated solutions for a lot more money, but this would be a start.
Good luck.
I'll second that. The Knox & Kane #58 will be a decent match up for the K-27.
I would suggest adding extra shielding around the optical sensor as outdoor conditions can sometimes confuse it. A plastic cup with a small vent mounted on the back side of the speaker will great improve performance. Also it will need batteries to run off of. I would suggest a couple of 3.7v Li ion cells (for 7.2v) like these - http://www.all-battery.com/2li-ion1865037v2200mahcellswithprotectionpcbwithtl100li-ionuniversalbatterycharger.aspx (http://www.all-battery.com/2li-ion1865037v2200mahcellswithprotectionpcbwithtl100li-ionuniversalbatterycharger.aspx)
will let you run all day and then some.
-Brian