No problem, take your time.
Mouse: oké, the G402 will work just fine for that. I use the G400s wich is roughly the same shape myself and do palm/fingertip myself. The review is amazing, so after you watch that you can see for yourself if that mouse would be nice for your use.
Keyboard: Right, well it all depends on what you want from the switch, there are a lot of options. Heavy switches prevent the accidental keypresses and are slightly more fatiging to type on. You also got clicky switches that make a very hearable click when you pressed it far enough down to register and then you have the tactile ones that give you a soft feel when you pressed it down. As for gaming, MX reds are considered to be the best, as you can very quickly double tap. But some people find them too light to type or game with as they are relatively susceptible to accidental key presses. MX clears are actually very rare and I have no experience with them. But seems to be just a slightly heavier MX brown. I personally use MX brown myself and really enjoy them. It's best to go to any PC store that sells mechanical keyboards and test out every single switch that they got available for testing. But MX brown, red or blue & black are the most populair switches.
Headphones/speakers: Oké, well then you can just leave the microphone out my list. For the headphones; rock and classical music are my favourites, so I listen to this a lot. I can tell you, these headphones are amazing for this music genre. Currently listening to this epic song from Two Steps from Hell! As for speaker suggestion, I also am not an expert on this edge. I personally have some simple 2.1 speakers myself that cost me €40 who work fine for when I want to relax and watch a movie or something in my bed. I pretty much use my headphones all the rest of the time. So I would very much suggest to buy headphones first, keep your speakers and see how much you make use of them. If you find yourself making use of your speakers enough to justify the cost for new ones. Then you can always PM me or go to other forums.
As for the money, my suggestion list is well under your $2500 that you had planned out, and as I said as well at the very top, it's possible to cut the costs down even further without hitting performance all to much. I would hit on the ease of use, silence, monitor, perhaps even storage (would add more, but reduce the SSD size). There are a lot of places to cut the cost. Just let me know if you want it to be cheaper and I can make it for you.
Also: I ignore mail-in rebates in my list, this is because the budget is asked "before mail-in rebates, shipping, taxes". So likely a few of these products got some mail-in rebates that you could make use of. Although I don't have this in Europe so I never dealt with this, I heard that some vendors are taking for-ever to get the money to you or that they only provide a check that you can use for their store. I don't know.