Nice looking room, i built my house with a seperate media room just over 2 years ago. Sound Proof walls, Floating raised floor, 120" projector, sound panels at 1rst reflection points , column style Bass traps, dual 18" infinite baffle sub system all done on the cheap (DIY) I learned most of it on this forum, great place!
av123 currently has a huge sale on their awesome 5 speaker Rocket package which I own and love, under $2K for speakers that retail for $3500. The mains (RS850s) sound is simialr to Paradigm studio 100's($2600 a pair) with a little cleaner bottom end and slightly better imaging IMO. The center the RSC200 nicknamed Bigfoot has a well known rep for being a monster of center size and sound.
Pioneer Elite, Marantz, Denon, Yamaha all make good receivers, i currently have Yamaha but will soon upgrade to a Pioneer Elite or Marantz. All good choices.
That tile floor is gonna give you fits to get clean sound, reflections can really muddy up the best speakers, you'll get the sound from your speakers (good) along with the same sounds bouncing off this and that all traveling different distances reaching your ears at different times (bad) Kinda like when you pull up at a drive through and you can hear the sound of your engine bouncing off the resteraunt wall.
You may think your center sucks because you can't make out the words when the whole time this is what's happening, your hearing each word several times within milli seconds all jumbled up.
Rugs and furniture do help alot, Accousitc sound panels are probably the best investment I ever made. I made them myself, but it really cleaned everything up they can absorb sounds much lower that carpet and rugs alone. It was like I had an entire new sound system.
Try the clap test, if you clap and you hear an echo (bad), if you hear a clap and then instant silence (good)
Many people overlook this but if you want the absolute best HT experience you can get, it'll make morre of a difference in your room than most any other HT decision you'll make.