My very first HiFi was a Marantz 1060 and Large Advents, a Philips 212 and B&O SP-12 cart. Since then I've had a bunch of separates, 150W/ch HK Citation 16, 40W/ch MC240. This time around I went with a Marantz PM7000N Integrated driving LS50s , now MA Silver 300-7 and a VPI Prime w/Hana SH..
If I were to upgrade, My next move would be a McIntosh MA-252 Hybrid Tube, above that, a Levinson 5802 or 5805 with a possibility of a Luxman 509. And I still haven't touched $1OK, and I haven't blown a European vacation on interconnects.
So if none of the above float your boat, and you gotta have separates, I'd start with Parasound, maybe NAD, and from there it's a 3-Way between your discretionary income, marital considerations, and how much fiddling around you want to do with components and cables.
For me, there's just too much value in integrated amps, and at the end of the day, I just want to listen to some music, maybe spin some vinyl.