Hi, Tushar and Dharamveer! I just wanted to mention that comparing the PSR-E343 with the CTK-860IN is a bit lopsided. A fairer comparison would be between the PSR-I455 and the CTK-860IN, or even between the PSR-E443 and the CTK-860IN (although the PSR-I455 would probably be fairest). For instance, the PSR-I455 and PSR-E443 have a pitch bend wheel (like the CTK-860IN), whereas the PSR-E343 does not. The PSR-I455 and PSR-E443 also have registration buttons on the panel for memorizing and recalling your favorite voices and panel setups. (The PSR-E343 also lets you memorize and recall setups, but recalling a setup requires pressing more than just one button.)
As for the volume of the sounds, for some reason Yamaha sets the default volume rather low for many of its voices-- in fact, none of them are set to "full volume" (which is even discouraged, I think because it might cause the voice to sound distorted or clipped)-- but you can modify the volume to make the voice louder or quieter. Note that I don't mean the "Master Volume" dial that controls the overall volume of the keyboard (although you can certainly adjust that as desired), but rather the volume of the voice itself, which can be set to any value ranging from 0 (silent) to 127 (loudest). Of course, setting a voice's volume to 127 doesn't necessarily mean it will play at the loudest volume, because if you have the Touch Sensitivity turned on then the notes might play at less than 127 volume (or "velocity") depending on how fast (or "hard") you strike the keys. Nevertheless, I can sympathize with you about the default volume of the voices being set so low for many of the voices on Yamaha keyboards.
The most important thing to keep in mind is that you should always try to play a keyboard in a store before you buy it-- including comparing two keyboards side-by-side if you're trying to decide between them. I would also add that it's a good idea to look over the manual(s) of the keyboard(s) you're interested in trying out, so you'll be in a better position to try its various features-- after all, you wouldn't want to discount a keyboard because you thought it couldn't do something (because you couldn't figure out how to do it in the store and the salesperson didn't know, either), only to find out later that it can do what you wanted. In other words, the more you learn about a keyboard and its features ahead of time by reading its manual(s), the better able you'll be to put it through its paces when you play with it in the store.
But perhaps the most important thing to remember is that you are the person spending the money on a keyboard, so you need to be sure to get the keyboard that you want, and not be swayed by anyone else's opinions. That doesn't mean you shouldn't listen to any advice or comments from people who actually own (or once owned) a specific keyboard that you're interested in, because they might have important feedback (either positive or negative) based on their actual experiences with that keyboard. What it does mean is that you shouldn't pick a particular keyboard just because a bunch of people recommended it-- since they aren't buying it, you are, and you're the one who's going to be playing it. So go ahead and ask other people for their advice and opinions, but don't make up your mind solely on that basis-- try to find a nearby store where you can get your hands on whichever keyboards you're considering, so you can see and hear them for yourself. It might also be a good idea to wait a bit after trying them out, to give yourself a chance to research them online, then go back to the store a second or third time (or as many times as needed) so you can try them out again after having read up on how to use them.
Edit: Regarding the warranty thing, I think the manufacturer should honor the warranty when you buy a new keyboard online and have it shipped to your home. However, that might not always be the case, as it might depend on who you ordered it from online (e.g., whether the keyboard manufacturer considers the dealer to be an "official qualified dealer" or not), possibly the country you ordered it from and/or the country you had it delivered to, and other considerations. Thus, if you're thinking of ordering a keyboard from an online dealer, it's a good idea to make sure that they're reputable and that the manufacturer will honor the warranty on the keyboard.