Must admit, although I agree in part with Silly's earlier comments re: floorstanding speakers (those of less than £500), I have to disagree at the same time!
Whilst sacrifices will have to be made in contructing a £300 floorstander, it doesn't naturally follow that the resulting sound quality is so poor as to be unlistenable!
Having owned a pair of Mission 733i floorstanders for ten years now (cost £330 new), I have to say I'd have a very hard time replacing them. Yes, without bungs in the bass ports, there can be substantial boom, but they are flexible enough to have the port either fully bunged, or partially (the port is bifurcated in order that half can be closed off and half left open), or can be sand-filled at the base to improve rigidity.
I haven't gone down the latter route, but the speaker is extremely musical, it doesn't favour one type of music over another and I listen to a very wide range - classical, rock, vocal, electronic (early Tangerine Dream, man!), hard rock (Motorhead - they still count!!) and so on and so forth. To improve substantially on that, I think I'd need to spend good money and no shortage of it either to better them. Hard to say without comparing like for like, but, why seek out a solution for a problem that isn't there?!
I'd suggest a potential buyer listens to both types - floorstanders and bookshelf/standmounters. I hear great things written of AVI's Neutron IV (or is it the V now?!) and would be well interested in those depending on what my room size was and what I'm partnering it with. It's a tough choice and especially at the £200-£400 end of the market. Q Acoustics have good things written of their products, KEF, Monitor Audio, Tannoy, et al, all have strength in numbers at that price point. A tough choice to be sure!