That example system would have cost around 6k new. Building speakers is fun and rewarding, but it's not a cheaper alternative for your requirements. If you're not in a hurry then maybe you should hire some equipment and see what fits your bill.

hmm i think i might be straying from the roots of the idea . The events are very wholesome / cosmic and experimental affair . Charlie who i do it with is an amazing musician / dj and sound designer and im from a woodwork punk background and i think it would be cool to build something sculptural and awesome sounding …. but i think im starting to realise without a huge amount of knowledge and experience , going off piste from plans and tried and tested methods is a bit of a recipe for disaster. 

It's worth mentioning that a lot of stuff on the used market was built before the price of 18mm bb grade birch sheets went from 30-40£ to 110-150£ as sanctions took a big chunk out of the market supply from russian birch.

If all you want is a decent small system, have a look at somewhere like Thomann’s active loudspeaker sets section of their web page. There will be likely something listed that will work, and is within your budget. With the amplifiers built into the cabinets there is less to move about and it simplifies the set up.

If you just buy a few random drive units, use a passive, off the shelf, crossover between the mid and top, plus a cheap analogue/active crossover between the bass and mid, you are very unlikely to improve on a commercial system.

With regards to the Martin system linked to, The biggest selling feature is the badge. The Blackline series is nothing special. It works as well as any other sub/mid/horn in a couple of boxes would, but it must sound better because Martin. It should not be that difficult to match this.

In my opinion, the system that Lucasdude uploaded a photo of would be more than enough for you current needs. The only reason for using a 12” or 15” driver in a mid/top cabinet is to give more bass output if it is used without a sub. With a 3 way system the bass cabinet does the heavy lifting. Acoustically, an 8” drive unit is larger at 100Hz than an 18” driver is at 40Hz. A smaller mid drive unit will integrate better with the high frequency driver.

To improve on these commercial systems, you really need to use a digital speaker processor (dsp), and then learn how to set it up, which, if you want to do it properly, means using a measurement microphone. There are plenty of free software programs on the internet.

If you are thinking of building more cabinets in the future, with a 2 in 6 out dsp, a 4 channel amp for mid/tops, and a 2 channel amp for bass, you could have a common amp rack with different presets for different systems.

If you are determined to build your own system the BMS 12S330 or Ciare 12.00SW, are a better option than the Volt driver linked to. For simplicity of mid/tops, an 8” coaxial drive unit would work well. I have used the BMS 8”, but I would imagine that similar units from B&C, Faital, etc would sound just as good.

3 x metres 2 core 2.5mm speaker cable £3.81

With 6 drive units, each cable is 0.5m long. How does that work? I would have suspected a typo, but Blue Aran's price of £1.27 per metre x 3 metres = £3.81 says not.

If using 4 pin Speakons with two drives in the top cabinet,  4 core cable would be a better option than 2 core. Using Blue Aran's price of £3.20 per metre, and a more realistic length of 6m each (still short), gives 24 x £3.20 = £76.80.

Personally, I don't see the point in quoting prices for second hand equipment. I managed to buy a low use Sennhiser wireless mic, with a 865 capsule, plus the receiver and case, for £40 off ebay. I doubt that is typical. Prices can vary considerably. Searching for the XTA DP226 bought up prices from £567 to £1200 on ebay. Given that the main aim of going the second hand route is to keep costs down. Even at the prices you quoted, your amp rack combo totals £1445.

Buying new (Thomann prices), A DCX 2496 crossover, TSA 4-700 and NX6000 comes to £883. Additionally it comes with a guarantee, and as a bonus, the total rack weight will be less than the weight of the EV amp. The badges on the second hand stuff might get you a few kudos points on forum like this, but in reality, at a gig, no one will care or be able to tell the difference.