As one of the lucky guys with an 8x10 enlarger I would recommend getting a 5x7 enlarger. A 5x7 will enlarge to 20x24 quite nicely. Prints larger than that are a real commitment.
If you come to love the contact print more than any enlargement I would go right to 11x14, count on your love to keep you strong, carrying it around. 8x10 is a compromise size for me. I'd swap my 8x10 camera and enlarger in a heartbeat for a nice 11x14. I may end up just building one.
Cheers,
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