After a quick search on sites like RS, there are some very good thermal grease products that cost less than most performs pc products (or at least for their volume) and seem to have a better thermal conductivity properties. Around 10W/mK compared to around 8 (according to an ekwb source. But I can't link as am posting from mobile).
What I'm wondering, has anyone tried these professional products. Or see any catch I'm missing?
RS thermal grease: http://uk.rs-online.com/web/p/thermal-grease/7742697/