Otherworld are excellent but I'm more Old World than Forgotten Realms! Pig faced orcs don't do it for me! Might get some of the other figs but not sure many blend with citadel and I can't afford all of them!
First of all, pig faced orcs eare great, no need to discuss this, because it's a fact.

The old citadel miniatures mix together very well with Otherworld. The man behind that company, Richard Scott, has the most complete collection of citadel's AD&D-range on this planet:

Part of the reason for him to start OM was to fill the gaps of that range.
I don't think a Porsche is cheaper than collecting the old scenario sets. Most of the figures from that ranges were part of the normal ranges and are not that expensive. So with each set there are not more than five miniatures that are really rare. Be ready to spend 50-100€ for each of the and you have reached your goal.
Okay, I've seen Gimbrin Finehelm being sold for US $355.00 on ebay last October, but I think the prices of that fellow have dropped after six of this miniatures suddenly appeared in Norway so that six greedy collectors were able to grab them. I was one of them:

Now he he is a hero within my planned army of 500 classic Citadel Dwarfs. And he was the 250th miniature painted up that project.

These days I am only missing two of nearly 350 classic Citadel Slotta Dwarfs. The Jolly Jape Dwarf and Dwarf Champion Mace 2. Any help appreciated.
It sometimes really is annoying that certain COLLECTORS only collect certain miniatures, because they are rare, which raises the price.
Most of the villagers and townsfolk sets are not that rare (and most of the faces sculpted by Trish Morrison are not that great).





The only range that really is expensive is the Townsfolk range from 1988. In my opinion the most beautiful range are the Travelling Players by Copplestone (that was were he peaked).
I think it's the right way to collect both classic and new figures if they are nice.