Dear Avinz,
HT which you used is a basic mass market HT package for normal users who don't care much about the supreme sound quality but enjoy their movies on TV with improve surround sound. Musical performance also would be OK with boom boom but not much of subtle details of the music. The one which you are trying to move to is a decent one compared the existing one where you get more control over your choice of inputs and better and controlled sound compared the Philips one. But, will it be room filling for 15 x 11 ft, I am not sure, you need audition the same. Philips was a tallboy kind of but these are small speakers. But, you will see improvement on the controlled boom boom.
As fellow FMs suggested, going for discrete components might be great in long term. But, if you are already running in budget constrain, then you might be missing out to the surround envelope of sound until you complete the 5.1 configuration. There are package of 5.0 from Taga which cost you around 40K which would come in budget and you can couple with an AVR and run without Sub for some time and then you can add it when you have a budget.
But, all these are purely based on your budget. Building a discrete system is a deep rabbit hole, which might burn deep in your wallet. Please be aware of that. Sometimes you may not be able to achieve the complete 5.1 itself due to budget. Please be informed that, this is just my personal opinion and not meant to offend other FM's discrete system build-up idea, and at the same time I am not at all discouraging you in doing that. I am just sharing the hard fact.
Since you asked about YHT-1840, there is one more model which YHT-3072, which has some advantages over the 1840. this was discussed in the below mentioned thread, which you can refer to.
Hello all, If we ignore the bluetooth connectivity in YHT-3072 how better is it than the 1840? Is it worth spending 20k more? Noob here and this would be my first step into the Hi-fi sound. Definitely looking to upgrade the speakers in the future. Regards.
www.hifivision.com
Following site, I found this YHT-3072 is listed. You can check it out. You can even check in nearby Reliance Digital showroom also. They might have it.
My apologies if I have confused you instead of giving clarity.