Domain for an ecommerce? Age,authority and more

Hi guys, my plan is to start my first ecommerce ever so any advice will help. My first question is about the domain. I have many great domains and most of them are used in my PBN, but none of them does not have any relationship with shopping. So my first option is to put the ecommerce on one of theese. Lets name it kliller domain. Domain have more than 300k backlinks from 300+ high authority websites. Domain is legit pr 7.
I also have aged, but clean domain about shopping (8yrs old, never used before, very easy to make a brand from it). Lets name it domain S
So here is my options

1. Put the ecommerce on the killer domain
2. Put the ecommerce on a subdomain of the killer domain
3. Put the ecommerce on aged, clean shopping related domain


The ecommerce will target local custommers. Search terms are under 500/month, and 99% of my competition is using adwords and facebook pages to bring traffic. So it will be no problem outrank them.
The killer domain was used for edu, society, governmental things, and also domain targeted local people, but like I said, nothing related with shopping.
Domain S is a global shopping domain, has no authority, no backlinks, only age.

Ecommerce will target local people, but will offer many different products. So which is the way to go in my case. Thank you

Use the domain name that will lend more credibility and repute to your site.

If it's local then having that local area name in it would be good too.

Domain should be short, branding and easy to remember thats the main requirement. You will gain authority factor eventually with marketing efforts and PR.

I am also working on my new online shopping portal

The domain should be something catchy. Maybe something that rhymes with whatever you are selling. Example - BeatsOnTheStreets.com

thank you for your answers, but seems that I need to specify more..
Killer domain is 3 letters .(my cctld) www.---.cctld (PR7, great bl profile but not related to shopping, 17years old)
Domain S is www.shop----.com (PR n/a, no backlinks, 8yrs old)
The difference in authority between this 2 domains is huuuuuge.

thanks