Sorry petrolhead, reading it back it doesn't make much sense does it?! The 460MG is more fiddley than the 804RC2. Firstly (but no biggy) manfrotto have redesigned the 'locking' quick release plate, it is much easier IMO to remove the plate from the 804RC2. Secondly the adjustment knobs on the 460MG are small little things butted up againt the joints of the head. They do work it's just that on the 804RC2 the knobs are extended out by metal rods and are larger in size. It just feels easier to adjust to me. Like I said I have the 460MG. When I bought this it was between that and the old 141RC2 which is over twice the weight and a lot larger in size. The 804RC2 is much lighter than the 141RC2 and is a little bit more compact. If I was making my purchase today it would be the 804RC2.
Going back to Kaoshan's comment about plastic heads, infact the 804RC2 is actually made of plastic. It's made of a new polymer called Adapto:
"Adapto is a special technical polymer that is comparable to aluminum in strength but is 50% lighter. Compared to metals such as aluminum Adapto is an ideal material for photo imaging equipment as it has superb resistance to extreme temperatures and will not corrode or oxidize. Additionally, Adapto is an excellent vibration absorbing material making the 804RC2 head an ideal companion to aMagFibre tripod for the ultimate in vibration free shots."
As for the tripod itself its a toss up between weight/cost vs max height/stability. The 190PRO + 804RC2 will weigh in at 2.65kg and will have a maximum height (with centre column down) of 131cm. Whereas the 055PRO + 804RC2 will weigh in at 3.15kg and will have a maximum height of 147cm. So thats half a kilo more to lug around for 16cm of extra height and more stability. Oh and an extra £30ish quid.
HTH
P.S I remeber reading some advise somewhere - "Invest in a decent tripod now and it should last you a lifetime"