Suggestions to improve sound

[Xantia]

I need some recommendations from the experts of AVforums about a possible upgrade of my system. Currently, my setup is composed of:
AV receiver - Onkyo 595 (no preouts)
DVD Player - Pioneer 757Ai (DVD-V/DVD-A/SACD/CD), connected to the AV through 5.1 output to get DVD-Audio and SACD sound. DTS and DD decoding using this player seems the same as using the Onkyo decoding.
Speakers: Front - Tannoy Profile 632 (monitors), Center+Rears - Energy Take 5, Subwoofer: Mirage FRX-S8 (100 watts).
Cables: straightwire+wireworld+QED
I also have a 2-channel amplifier (Denon PMA-480R) that is not being used.

I find the quality of sound not very good, at least for audio only. For HT, the system seems reasonable.
I would like to significantly increase the quality of sound (more detail, tighter bass, more tridimensionality) but I dont know what would be the best upgrade path? Here are some options, so please comment on that:
1- Add a reasonably priced AV processor (Rotel RSp-1066, Cyrus AV8, Outlaw 950) and use the Onkyo as amplifier.
2- Change center and rear speakers to Tannoy (tannoy mercury mx?).
3- Change all speakers (suggestions?) except the subwoofer.
4- New and better AV receiver (Denon 3803?) with preouts in order to also use the now unused 2-channel Denon amplifier?

Which solution (if any) do you think would give the best improvement?
I would appreciate it very much your input. Thanks.

Rui

[Nobber22]

Dump the Onkyo completely and get a new receiver (like the Denon) first. Also using the Onkyo with a good processor is not doing the new processor justice. A processor deserves a quality 5 channel power amp.

Also get a matching set of speakers across the front soundstage. Move the Tannoys to the rears.

[wilber]

My tip would be to go for a new av amp from someone who will give you a "money back if you don't like it" guarantee. Take it home plug it in and see if it sounds better, if it doesn't take it back and it won't cost you a penny more than the cost of your petrol.

BTW I think that Tannoy Mercury speakers are very good value for money

You came to the wrong forum, this guys never heard Onkyo, they think Denon rules...