Sorry but no sub £500 "active" monitor is going to be neutral at all spl levels. An amp is an amp, it's not relevant where it sits physically with regard to it's quality. There are a lot of audio quality issues relating to physically placing amps inside speaker cabinets but there are of course some audio quality benefits, as with everything there are pros and cons. But ultimately the pro of active speaker amplification is far outweighed by the actual quality of the amplifier, and the amplifier in any £250 set of active speakers is going to be a long long way from perfect.
And those Alesis are not going to "kick out" anywhere near a flat sound either at that price point. If by "Hi-Fi" speakers you mean your average £200 JVC etc that most people would have in their homes then maybe they are a bit bass heavy. But many are the complete opposite, you simply can't generalise like that. True audiophile speakers try and balance absolute neutrality with good dynamics. This is always a compromise as the laws of physics dictate that the higher the senitivity of a drive unit is the narrower, (and often more uneven), it's frequency response is.
Studio montors aren't actually built to be "accurate" despite what all the speil you might read about them might say. They are designed to be "revealing" to allow the engineers to be able to hear what is going on in the mix and to be able to play very loud. To this end they are nearly all, (bar the extreme top end custom built designs), bright in the midrange.
Final note, a speakers final tonal balance is heavily dependant on the environment of it's use. Speakers interact with their surroundings. A speaker that may be bass heavy in one room will be neutral or even bass light in another and vice verse.
Oh and a final final note.. small speakers, (by which I mean anything that isn't at least a meter high floorstander), are incapable of being "accurate" , (even in terms of frequency response), over the the entire audiable spectrum. Very few speakers on the market today have any significant response as low as ,(let alone below), 40hz. The majority can't even produce a Bass guitars E string fundamental at the correct level let alone its sub harmonics.