Hi there,
Yes, there is a difference. You will be best served, (and frequency matched), by getting the matching sub.
Take my word for it or search these forums for "monitor" and "professional". Like most things in life, it boils down to "you get what you pay for".
Some other things to consider -
- How big is your room? If it is smaller than 2550 cubic feet you literally don't have enough space to generate the length of sound wave necessary to properly provide even sub-bass.
- Do the Tannoy Reveal's have a low-end cross-over frequency switch/filter? If not, you will also need to buy a crossover to achieve some sort of flat response. The sub will normally have a defineable crossover point, but if your monitors don't then they will also still be pumping out the noise in the sub-area. This reduces their performance, clarity and accuracy.
- Have you acoustically treated your room? If not, then it will not be uncommon to see peaks and dips of +/- 20dB within any range of 10-15kHz anywhere in the spectrum, but particularly noticeable in the bottom end.
The downside here is that acoustic treatment below 150Hz gets hard. It is simply really, really difficult to properly handle bass boom effectively in this area. So while adding a sub will give you louder bass, it will also lie to you even more than your current monitors.
Heard of room modes? Or even the dreaded "Standing Waves"?
Simply put, when a certain frequency is played in your studio or mixing room, it will create a sound wave which is an exact match for either the length, width or height of your room. This will only happen at certain frequency points and not all. There are plenty of calculators which can show you where your room will have these sorts of issues. Do a google for "room mode calculator"
Basically what it means is that you end up with some notes being way LOUD, while others, (which are hitting a reflection of themselves and flatlining), can't really seem to be heard at all. Use a tone generator to make the sound of one of the frequencies identified in the room mode calculator, (use one somewhere between 40 - 90Hz), and take a walk around your room. You will hear places where you get a whole lotta bass and others where you get nothing.
Plug in a bass guitar and play through an E scale....do you get something like this?
e f# G# AA b c# d# e
My "A" used to stimulate a room mode and I would get a real big boom on it. Your note may be different. But either way, it's not much fun when trying to set up a mixing position and trying to hear whether or not the kick needs another couple of dB or not...
So, "learning how the system translates and mak(ing) the necessary adjustments", could be a pain in the arse if you don't have a good grip on your room.

Q.
Trust me - I learnt the hard way.....