Well, upping the game to the bigger 27"mac is a slippery slope, a 21.5 with 8g ram and 1 TB SSD is $2399, the entry 27 iwith 1TB SSD is $2499, plus 3rd party ram @ $107 (that could be put in later). Then there's the high end 27 for $2299 right in the middle but with a 2TB fusion (that would bring the SSD part to 128g) I can't see getting a BTO without a 1TB SSD because I'm at 85% full now with a 1TB HD. and with needing to purchase an external for the Photo Library(502GB) it would not be a big cost to keep all on one SSD in the machine......That's why I posted why not just get the 121.5 @1499 and expect a little less life and have $800 in the bank for a new mac in about 5 years if needed....Desicions, DecisionsOK, first off I would not buy a new iMac with the 1TB Fusion Drive option because it is a poor value. The current 1TB Fusion Drive only has a 32GB SSD, where as the original one had a 128GB SSD. I recommend springing for at least the 512GB SSD instead and simply using a 3.5” external drive for much greater storage. As for RAM, I recommend the minimum being 16GB.
Such a configuration should give you many years of fast and reliable service. Apple is supporting most Macs for 7 years on the software side. I see no reason why it wouldn’t serve you well for that long.
All that said, you sure want the little iMac over the big one?