I would be grateful for any suggestions re: a solid performing centre speaker that could potentially be a good match for an Onkyo 506 or 606 AV receiver.
Maybe you need to ask a different question - ÿwhat would be a good match with your existing SPEAKERS? ÿNormally, it would be the matching centre from the same manufacturer.
Indeed!! Being very much an amateur at all of this, am I right in thinking the 3 front speakers as it were, should preferably be from the same manufacturer and range?
Well if music is not too much of a concern then I have always liked these. You could also look at Superfi as there are many packages listed on there within your budget.