Drupal and Postgres for complex search site

I am new to the group but a long time developer of CMS usually based on PHP/MySQL.

I have a new project to manage, which is going to need to be driven by a postgres database due to a second process running on the same database.

The site will require all of the below and many smaller attributes and I need to know whether there are suitable developers who can work this out with a Drupal/Postgres build or whether this is better developed outside of an existing CMS such as Drupal, Wordpress, Joomla et al as a bespoke CMS project based on a postgres database.

It is a parts locator website that has at any one time over 600,000 parts listed. these parts are searchable and filterable initially by the standard Make, Model, Year and then by 6 or 7 more narrow choices such as body type, etc.

Once a part is identified, right wing mirror for a bmw 325 from 2008 for example, then the vehicle wreckers or other site users with the right to list can be contacted through the site.

If a part is not discoverd for a particular search then the user has the ability to send requests to all vehicle wreckers who have identified in their profile that they deal in that vehicle type.

The site has 3 or 4 different levels of user, and all actions by each user, such as searches carried out, requests made should be stored as a history, both for the site user to see and the site administrators to see and analyse.

The site also limits the number of parts each wrecker can list publicly at any one time, but can allow him to choose from his entire stock that he has uploaded, the max number of parts he is allowed to display according to his membership level.

Finally the site also provides specifically formatted files that are loaded directly into software to create the magazine that is sold throughout Australia.

Finally the site has to integrate a second database. this database knows which parts are interchangebal between vehicles. So a search for a wing mirror for a bmw 3 series will initially return all the bmw wing mirrors listed, then the interchange database will provide the part details for identical parts that might be from other manufactureres or from other bmw ranges. So, as above, the 5 series wing mirror may be a direct interchange for the 3 series wing mirror. The site search should then display these parts as iff they were the 3 series wing mirror assembly as well.

As you can see the site is quite specific, the design and wireframes are quite complex but well advanced and a preliminary database minimum structure has been defined, but is not restrictive if deemed to be unsuitable.

The current database of current and historical parts runs to about 8GB at the moment but is 450 odd tables of which only around 200 are used. The original site was developed by a very poor developer and the administration screens I have seen can take 5 minutes to load. The site owner is extremely keen that the site is quick to use both for the admin and the site user. I envisage that ajax will be used in the search and we have considered an Apache/SOLR server but do not know if this will integrate with postgres.

We will be looking for developers very shortly, but need to know whether this users of this Drupal group belief Drupal is an unnecessary complication or a perfect fit?

thanks for your help.