No probs Cara, that's what this Forum is all about. :t:
The 701HDV head is a good head for sure. you shouldn't need to change that for general viewing, most who use the 501 do so because they are into digiscoping which can add significant weight to the whole lot and obviously throws off the balance.
In answer to your first query, yes the 055 legs
are that much better, comes with the territory of the increased price tag. You can find a list of current Manfrotto tripods here along with there specs to help you choose
http://www.manfrotto.co.uk/category/8374.58969.0.0.0/Tripods and if you look carefully at the lists you'll see a button that converts the specs to imperial. Another important factor is how tall you are, in the specs you should see measurements for the maximum height of each tripod with the centre column down which is the key one. Ideally you'll want to be a little bit taller than that measurement (don't forget the extra height of your head and scope tho), that way you can quickly extend all 3 legs to their fullest and you won't need to be fiddling with adjusting them to suit your height. So no offence but if you're a wee shorty then the 055 legs may just be that bit too tall and not very suitable. You'll have to gauge that from the specs.
Which brings me to your last query, if the 190 legs are more suitable in height terms then that should take priority over the better capabilities of the 055 legs in my view (others may disagree) and you could indeed get some CF versions of those and yes CF is sturdier whilst also being lighter than aluminium, a big improvement (and don't feel quite so bl**dy nasty to use on freezing cold days!
).
However I also mentioned the Giottos which I would say have superior CF tripods of similar height to the Manfrotto 190 range. I hear good things about the Giottos MTL8361B CF tripod (rated to 17lbs too!) which you might google and give a look. Also be sure to check out the rest of the Giottos range as they are a good brand that often gets overlooked.
Cheers. B
Adam