Your Xeno is going to be a cannon with a 14500... I have a black E03 with a neutral T5 and it screams. Keep in mind that the E03 is not regulated, so it will get steadily dimmer as the charge in the cell depletes.
Quark AA is a good choice, but if you've already got a neutral light and you like it, you may very well not like the cool tint of the Quarks. They are also very inconsistent in their tints; you never know what you're going to get. You really do play the "tint lottery" with their lights.
Thrunite Neutrons are supposed to be screaming bright on 14500, but they've had some significant quality issues... do a search for 'wobbly head' and you'll find a lot of reports from members here complaining that the threads between the head and body are loose, and there have been several reports of a UI bug in them as well.
The Spark SL5's can run on 14500 and are nice lights. Well made, choice of XML or XPG emitters in cool or neutral in both emitters. They're about the same brightness in either neutral or cool. If you want a more throwy light, get one with the XPG, if you want floodier, get one with the XML.
There are several other brands that make nice 1xAA lights, but most uses cool emitters instead of neutrals, and I'm a tint snob, so I don't pay a lot of attention to cool tint lights. I only buy neutral or high CRI lights anymore. YMMV though of course.