Much depends on the sort of music you're recording. You mention a flat and my heart sinks a bit - hard for you to work in and hard on the neighbours too!
Bass is the tricky bit really:you have to move a large volume of air by quite a large displacement (4" dust extractor?). Seriously, anything below 80Hz takes you well out of the range of 'bookshelf' designs, into floor-standing or stand-mounted enclosures. You *don't* need high power handling - 100-200W/channel is quite sufficient for things to get ear-damagingly loud.
Personally, I'd look at getting a pair of something decent-but-broken from eBay and repair it. Drive units cost the same whether they're going into new cabinets or old ones, but refurbishing something means the basic stuff is right. You might also consider an active crossover (i.e. before the power amps, not in the speaker itself). They're easier to tinker with afterwards, and cheaper to make (probably).
There are some classic designs around - the Yamaha NS10s*, BBC LS3/5As and LS5/8s (if you have the space and the wallet). I had a pair of Monitor Audio MA7s for years, which were good at the really cheap end. They've gone somewhat up-market recently though.
You want something that shows you accurately what the audio is, and doesn't flatter it. Many "HiFi" designs are nothing of the sort - they flatter the sound, and don't have enough detail to tell you what's going on. I spent years using 3/5As professionally, and still have a pair as my "PC" monitors for rough mixes. Above 120Hz they're wonderful speakers, but below that they're wholly untrustworthy. Amongst the classical engineers I worked with there was an unoffical rule:if on location with 3/5As, don't ever touch the bass! The result otherwise was a rescue job later on!
As you get into the range of about 100Hz downwards, the room itself will have a big effect. If you look at photos of BBC general purpose studios, you'll often see the monitors arranged very close to the mixer's position. It looks odd, as it's definitely not how home HiFi is usually set up. It's partly for space reasons, but also so that the direct sound from the speakers overwhelms the sound bounced round the room. The thing you often
can't see is that the speakers may be upside down. This is so that the tweeters are at ear level, rather than above the mixer's head! This is/was very common in trucks too, and there were at least two designs of BBC monitoring speakers designed to be upside down, and non-rectangular, to hang from the ceiling in smaller spaces (one version of the LS5/1 and a rare, wholly asymmetric and 'handed' variant of the LS5/8).
One trick:for 'nearfield' monitoring, to get a good, stable stereo image, arrange the speakers so that the tweeters are at ear level, and their axes cross in front of your nose (by about 6", more if they're further away). You'll be surprised how much better this is than the standard advice of your head and the speakers being corners of an equilateral triangle. The reason is that as you move side to side, the speaker you get nearer to goes more off-axis, and the one you're further from you line up with. This slightly compensates for the level difference, and the result is significantly better stereo.
Test your setup with a single, well-recorded male voice, just speaking. Poetry or a reading from a book is good, and at a volume only a bit higher than real life. It helps too if you know the person concerned's voice, but it's not essential. If that sounds natural, so will other things you record, rock and classical and speech.
On the other hand, if you mainly record modern clubbing 'music' all bets are off - you need therapy rather than monitor speakers
Hope that's entertaining, even if it's not useful!
E.
*I don't
like NS10s - too 'nasal' for me. They improved the drive units half way through production, which helped a bit, but the traditional fix was to stick loo paper to the case so that a sheet dangled down in front of the tweeter. I don't think it helped much but at least you could draw faces on it! Anyway the problem was nearer the crossover, and the loo paper didn't help that.
