Early 2011 to Mid 2012 MacBook Pro 15" non-Retina
Within the MacBook Pro line, there's two big cutoff points: the switch from a dual core in early 2011, and the introduction of the Retina line in mid 2012. For sake of rough comparison, we'll separate things out into these three categories.
Model | Passmark | Cost | RAM upgradability? | Storage upgradability?
Latitude E7450 | 3400 - 3798 | ~$270 | Yes | Yes
Late 2008 - Mid 2010 | 1540 - 2846 | ~$190 - $240 | Yes | Yes
Early 2011 - Mid 2012 | 5460 - 8454 | ~$330 - $520 | Yes | Yes
Mid 2012 - Mid 2015 | 7369 - 10202 | ~$590 - $1120 | No | Yes, with some SSDs
Comparing the E7450 to the MBPs, it falls into this weird gap performance-wise between the dual cores and the quad cores with the rMBPs well above what you need, since it's a newer dual core without hyperthreading. Purely for future usability, I'm going to recommend you spend the extra bit and get a lower end quad core.
Note that the performance of the rMBPs actually overlaps the standard MBPs, since they were released simultaneously with the same processors. Besides the upgraded screen and lighter weight–things that seem to be unimportant to you–the early rMBPs seem to offer little advantage, while carrying a price premium, having less I/O, and less upgradability. As such, I'm going to recommend you stay away from them.
Depending on what model you get, you'll probably want to upgrade the RAM and storage to match your reference laptop. Both of these are user serviceable on the unibody MBPs, and can be easily serviced following the appropriate iFixit guide. If you're not using the optical drive, you can also swap it out for a secondary HDD or SSD. Note that there are some issues with SATA III compatibility to be aware of, but these are general non-issues if you're careful.
Note that prices are approximate based on recent eBay sold listings. As with any complete system, finding a reasonable price on a used machine will take some patience and searching on various sites.