I was curious about how GPT-NeoX would match up to GPT-3. It seems like the most capable of the freely available models (at least based on their specs). Of course more parameters != quality of their dataset, so I can't really conclude much in this scenario.

As far as I know, https://textsynth.com is the cheapest host and NeoX-20B model is cheaper than OpenAI's Curie. They have a Playground which allows you to experiment without an account.

Re Stable Diffusion:

Based on the results I've seen in https://news.ycombinator.com/item?id=33038117 and other services, if you just want some eye candy I think Stable Diffusion would work fine (and is much better looking than anything DALL-E could generate).

However I wasn't impressed by SD's ability to understand the meaning of my sentence, it seems to just create an image by mashing words together (and sometimes even ignores key words/meanings). According to commenters, DALL-E is much better at "understanding" sentences so if that matters for this site; then I guess you should avoid SD.