Then I came across an article about the hardware Etsy.com uses and it was not as massive as expected. I was imagining at least a small datacenter...but it is not the case, and the whole etsy.com probably fits in a single rack.
I have also watched the piratebay documentary and my jaw dropped when I saw how small the hardware was.
So today I decided to do a few tests...
I thought why stop at 80k? So,I have loaded 6.000.000

Did it work well? Not really, so I decided to investigate!
looking at catalog/model/catalog/product.php I can see that opencart uses LIKE in the database queries
At first I thought this is not the best option and it does returm poor results as well so I will use RLIKE instead
opened the terminal and did a few tests.
The absolute horror!!
product table query SELECT using LIKE on the description took 2 minutes to complete.
product table query SELECT using RLIKE did in fact return better results, but need 10 minutes each to complete.

Looking at the product table I discovered that the name is indexed but the description is not!
So I did a fulltext Index for the descriptions and around 1 hour later I tried again.
product description query IN NATURAL LANGUAGE MODE LIMIT 500 took 0.326 seconds.
Not bad at all considering the size of the database.
product description query IN BOOLEAN MODE LIMIT 500 took 0.011 seconds.
I said wow and I was about to start jumping up and down....but then I tried an INSERT and landed back down to earth.
I waited 25 minutes to insert 1 product before killing it... so who knows how long it would take, the fact is that the store with 6 million products is not possible with the standard opencart, or in fact with any other of the free carts (and probably the commercial ones too)!
How about InnoDB?
I converted the product table to InnoDB and tried again....
IN NATURAL LANGUAGE MODE LIMIT 500
Result 0.928 seconds
not bad considering it searched 6 million products but it is 3 times slower than MyIsam.
IN BOOLEAN MODE
LIMIT 500
Result 0.352 seconds again much slower than MyIsam
So, time to try the INSERT...but guess what? same problem....it takes for ever!
A the end my conclusion is that for small stores with just a few thousand products will be faster if Indexing the product description without affecting the INSERTS too much (I guess around 30 seconds for an insert), but I'm not sure about edits or mass inserts because I was disapointed from the results and could not be bothered testing the standard thing any more. The test also show that MyIsam has faster SELECT than InnoDB...so not such a bad choice for shoping carts as some pople believe. For me, the speed is more important than the transactions support in InnoDB
Then I decided to put a bit more effort and bring in the reinforcements (the Sphinx).
Sphinx makes its own special search-optimized index and does not need a MySQL index to work.
The sphinx index took under 15 minutes to make the index which is impressive because it is 1/4 of the time MySQL needed to make its own index.
A quick test query showed that Sphinx can do the search in 0.018 seconds which is nearly as good as the BOOLEAN MODE query in MyIsam but there is no MySQL index in the product table, so INSERTS do remain fast.
So at last it is actually possible to have a functional opencart store with 6 million products but it needs work.
To use Sphinx you will need a vps or dedicated server and somebody who knows how to set it up... it did take me 2 days to figure it out, but it is more than worth it.
So....for me sphinx in the way to go!