Any update on your decision making process..?
Well next weekend i`m going to one of the music shops which kef said.
To get some advice and see how the speakers perform.
Try some of the high end stuff while you are there
it will blow you away 

Love my Wharfedale Diamonds...driven by an onkyo 9155, IIRC I spent about £300 as well.
I was inspired to get them by my old man's ~£300 NAD amp and ~£500 Mission floorstanders and how good dedicated amp/hifi sounds - and tbh despite costing hundreds of pounds less each, they're not far behind to my ears. Lack some clarity in comparison at high volumes and obv bass isn't quite as good, but good enough for me!
The volume at 40% on the amp is what I'd consider 'LOUD' and though I've only pushed it to 60/70% ish the speakers didn't lose any detail yet despite being almost deafening
Reason why your diamonds can be quite bass heavy is their location. (up against a wall and enclosed by shelving) All this will lead to elevated levels of LF. DBFB is sony's loudness function which boosts sub 100Hz by a predefined amount. The level usually falls as the volume control is turned up as it is governed by a tapping on the volume control. (referred to as a loudness tap) Past a certain point on the volume pot scale, there will be no loudness effect.
I still stand by what i said before, if you want a well rounded sound on a shoestring, go vintage. I'm not saying the wharfedales are poor, but they can be bettered for less money at the cost of looks and size.
Reason why your diamonds can be quite bass heavy is their location. (up against a wall and enclosed by shelving) All this will lead to elevated levels of LF. DBFB is sony's loudness function which boosts sub 100Hz by a predefined amount. The level usually falls as the volume control is turned up as it is governed by a tapping on the volume control. (referred to as a loudness tap) Past a certain point on the volume pot scale, there will be no loudness effect.
I still stand by what i said before, if you want a well rounded sound on a shoestring, go vintage. I'm not saying the wharfedales are poor, but they can be bettered for less money at the cost of looks and size.

The reason for vintage speakers doing well in the bass department is that the midbass drivers are usually 8-15" in size vs modern speakers which are 3.5-6.5". Same story with cabinet sizes. The modern speakers make up for the displacement deficiency by porting the cabinets and using multiple drivers, but you get vintage speakers that are ported and use multiple drivers. I won't deny that tweeter technology in particular has moved on a fair bit over the years. Woofers have come some distance but not a really long way, you can get much more bass from smaller speakers than you ever could before.
Speaker wise, if you can afford them i'd look primarily at celestion ditton 66 or 44, kef concerto, kef reference 104, tannoy monitor gold and B&W DM4. (most of these are really high brow, and will probably still cost quite a sum now) I wouldn't dismiss modern speakers either, but look around for a good deal and definitely audition them as speakers are the biggest factor affecting the sound of a system. (and it's best you buy what you like the sound of)
Vintage amps, whilst excellent sounding are more prone to failure if they are left unused for a long time, so unless you want to start dabbling in replacing capacitors, i'd stick with modern kit like that yamaha.
)