I went from MA-4 interconnects to MA-6 interconnects and SP4 speaker cables to SP6 speaker cables, over the years. I thought they all were very good.
I'd used them for the last 4 years or so.
This year I finally decided to do some major upgrading. I used the Cable Company lending library to try out LOTS of cables to try and better the Morrows.
A lot of cables I tried (interconnect, speaker, power) had different attributes and trade offs but it wasn't until I hit the big price points where I started getting definitive improvements. System synergy has lots to do with it, especially your speakers, but I didn't find a whole lot that compelled me upgrade from the Morrows. I eventually did, and it co$t me!
For what it's worth I borrowed cables from Silent Source, Shunyata, Cardas, Wireworld, Audioquest, JPS Labs, among others that I can't recall, and in most cases the upper tier of those lines. My favorites that I could definitively say bettered the Morrows were Audioquest and JPS Labs, but at prices that were at multiples of the Morrows.
That said, the Morrows aren't perfect, but I wouldn't hesitate to use them in a lower priced system if I were setting one up.