Hi Pathan 07,
Like Scott has suggested, if you were to seek feedback about a particular brand or model, there is a very good chance you will get some feedback from members of this forum who own/have owned that particular dob.
A number of us on the forum own an SDM telescope. SDM stands for Size Does Matter, and so, as the name suggests, this manufacturer works on large scale dobs. I believe he has a 40" in the pipeline, although on the SDM website the largest you will find to date is about 32" (
www.sdmtelescopes.com.au ).
In all of the years that I have been involved in this Noble Pursuit of ours, I have never come a across another maker of big dobs who comes anywhere near to being as good as SDM. And, as a local producer, Peter Read is able to provide post-sales support like no one else.
Obsession Telescopes in the US are the biggest makers of big dobs in the world, and the quality is very good. However, they are on the other side of the world, so postage and handling is likely to be over the $1000 mark (when I made enquiries 6 years ago, it was going to be about $1,400, not sure what it would be now), and you have to pay GST as it is over $1,000 in total cost. I know of one Obsession which has had to be rebuilt by SDM because it did not withstand Australian conditions.
There are many mass-produced dobs available on the marketplace - eg Meade lightbridges, Skywatcher, Orion intelliscopes etc, all of which have proud and happy owners on this forum. These are generally reliable, and a lot cheaper, but you get what you pay for.....
Good luck with your decision-making!