I currently have a 15 in mid-2010 MBP. 2.53 GHz Intel Core i5. 500 GB SATA Disk. 8 GB ram. Antiglare screen. Runs perfectly with Mavericks installed. It's in very good shape. Gazelle is offering me $430. Would it be worth it to take this offer and upgrade to a new 13 in rMBP with these specs: 2.4GHz Dual-core Intel Core i5, Turbo Boost up to 2.9GHz 8GB 1600MHz DDR3L SDRAM 256GB PCIe-based Flash Storage Is this upgrade worth it? Could I get more for my MBP?