Just look for a decent HU on kijiji or something, what ever suits your needs/liking and buy the kit/hardness from walmart.
you can probably find a HU for 50+ from kijiji, or one get it from bestbuy/walmart if you don't trust used ones.
If you're looking for just aux feature then bestbuy/walmart has some for around $70+, I didn't think I need bluetooth before but after I got this HU, it's pretty convenient.
Kit and harnesses are basically all the same, as for headunit, w.e suits your needs
I got all of mine set up for under $100 (if I upgrade I would look for a HU with a higher band equalizer that also still has bluetooth, aux, colour options)