Yes, personal taste is definitely a factor. But I suspect the tailors will have views on what is an acceptable range for the style described in my first post. Again, my apologies if outside the scope of the thread.
I realise this question may be regarded as falling outside the scope of the thread, in that it a general question without pictures.
However, if 'within bounds', I would be interested in the tailors' opinions on how to determine the proper size for a trouser opening, assuming a conservative non-'slim fit' non-heavily tapered style.* (It would help settle a debate I've been having with someone who favours a heavily tapered look.)
For a US size 8 shoe, around...
Loake 1880 (and only 1880) offer excellent price:quality at the lower end of your budget. Some of the ill feeling is about the lower ranges, which do indeed use corrected grain, are made abroad, etc. See: http://www.styleforum.net/t/354125/loake-appreciation-shoe-p0rn-thread/0_50
Herring Shoes (a mail-order retailer) are excellent. The have an own-brand shoe made by Cheaney, slightly over your budget, with the sleek last you are looking for:...
Dark navy (or midnight as suggested above). More elegant and appropriate to social occasions than charcoal grey. Indeed if I could only have OneSuit, it would be navy (with brown horn buttons, so capable of being 'BlazerSuit'-ed - search for Manton's thread).
I don't think we can really answer this question for you: If you consider you can continue with the functional style of dress without significant downsides, I would do this without hesitation. (Wearing dark worsted suits on the London underground in the Summer is enough to make me feel uncomfortable!) I would also acquire a tropical wool suit for occasions where more traditional business dress may be appropriate (as suggested by Macallan).