So I bought a new i5 iMac with fusion drive for an employee thinking it would have sufficient performance. I upgraded the ram to 24gb. She was let go about a week ago and I've been using the machine myself since, its underpowered for our creative needs and it's clear to me that I should have gotten the i7 chip with SSD now. Is my only option to sell the machine and buy a new one with the specs I need? If so, what would be the best venue to sell a 2 month old Retina 5k iMac? Craigsist, eBay?