I need a website directory website built on a good platform that is scalable

General information for the website: I need a directory website that is built on a good platform that is scaleable
Kind of development: New website from scratch
Description of requirements/features: I am looking to create a website directory that I can use to sell listings on. It is a wedding directory that will include Venues and Suppliers. This quote includes 2 phases - I only want a quote for phase 1.

Suppliers - e.g. A wedding photographer will have basic contact information and a photo gallery etc
Venues - e.g. Hilton London - will have more advanced information and fields

Phase 1 for the project I need a minimum viable product which is capable of handing 10,000 - 20,000 listings, with multiple back end users. For the initial project I only need admin users to be able to log in and add listings. In time I would like people to log into their own front end area where they can log in and update listings, add events to the website etc.

I'm currently putting together a wireframe design in Balsamiq and I have a branding consultant putting together a logo design and brand guidelines. The quote I need is for website design and back end build.

Website Functionality - Phase 1
Built on one of the big CMS platforms preferably Wordpress
Ability to create my own supplier category listings
Ability to create own menu structure
Ability to add own wedding and supplier listings
Ability for venues and suppliers to offer events and special offers
Ability to create new landing pages
Fully Mobile optimised
GA Integration
Blog - simple 2 column design
Search - To search venues and suppliers
Custom Header and Footer - in line with design
Integrated Mailchimp email Sign Up
SEO Friendly, Full control over meta data, page urls, etc
Written with SEO in mind, H1 titles for venue name etc
Map Integration
Captcha or similar on all forms
Forms on each venue and supplier page. These to be sent to a nominated email address, e.g. Each supplier can be sent own enquiry

Phase 2 - This is out of scope for the quote but will include
Payment Gateway and SSL
Review Integration
Venue Comparison Facility
Customer Web Login Portal – ability to amend their own listings
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