Puritan 136 vs 156 for simple system

@temmple - Go for the Puritan… 

OP: What I am wondering here is would it really be worth it to upgrade to the 156 over the 136?

I'll stay within that parameter.  I've the 156 and it is terrific.  Upgraded the power cord to Furutech 4.1 which made an uncanny improvement.  Not that you need go so extreme, but upgrading the stock cable will garner improvement.  Good luck.

The 136 is still in the running for sure. Just need to find a used one.

@temmple - As an aside, I was finally able to find a used ultimate power cable. I was expecting a minor but worthy upgrade. I was wrong. As soon as I replaced the classic power cable with the ultimate version, my system sounded more expansive, more detailed, and with better base. 
 

Keep checking this site and US Audiomart. They come up there every so often. Easy to pick one up at a discounted price. 

Puritan 136 would be a solid ground for any future upgrades, i have the 156 for few months and i can say that i can't listen to my setup without it anymore , separation and clean background improvement is very clear after months of use, One thing i did, is changing the Puritan power cable, it was too much of filtration for my taste, Puritan is a very good investment for the long run.