K7 mini. No experience with this light, but I hear it's an excellent option (perhaps the best) for small (10-15 or less gallon) systems wishing to stick to a tight budget:
https://noopsychereeflight.com/products/k7mini
Kessil A80: Yes, I am a kessil fanboy. This is the fixture I'd use for a small system, especially a cube. The link here includes the gooseneck mount, if you DIY mount yourself you can just get the fixture and save a few $. I use the H80 (different spectrum for refugium, same fixture otherwise) on my frag tank fuge, and made a mount myself for more control over mounting height, photo below:
https://amzn.to/42ZCGYl
AIPrime HD. Again no personal experience, but have heard great things. This is gonna be outside of your budget for a new one, but here's a link to a used one on ebay:
https://www.ebay.com/itm/3054042501...iS80UtKpswjLotnTSwE7EcH0fh4imMERoCTFIQAvD_BwE