Does it make sense to invest in a Blu-Ray player when it is connected to an Avant RF 100hz?
Will it clearly show a better picture quality?

A CRT based TV has just 576 image lines while Blu-Ray/HD has a minimum of 720 image lines. So a CRT has no possibility to show the image potential of Blu-Ray. Or do I see something wrong?

And what about sound quality ? 

Noelke:

Does it make sense to invest in a Blu-Ray player when it is connected to an Avant RF 100hz?
Will it clearly show a better picture quality?

A CRT based TV has just 576 image lines while Blu-Ray/HD has a minimum of 720 image lines. So a CRT has no possibility to show the image potential of Blu-Ray. Or do I see something wrong?

Sound quality will be better with good speakers. The picture quality will be more vibrant than a standard definition disc. However, I doubt whether the image will be better than an SD DVD on your TV. ie. the improvement will be negliable.

Blu-ray discs are very expensive and, here in the UK, rarely discounted by much. For example, I was in Zavvi (www.zavvi.co.uk) at the weekend and many recent SD DVDs were £3.99 each. Blu-rays were 'discounted' down to £14.99 for the same movie. I ended up with five SD DVDs at £2.99 and £3.99 each. I figured the same Blu-rays were £75!

I only buy Blu-ray discs if I know I'll want to keep the film and I'll watch it more than twice. If not, £15 each time is an expensive purchase.

On a lark I attached my blu-ray player to my Avant and found that the image quality was barely different, but motion didn't seem as smooth. I can't say why that would be, but I would say that for many reasons it's not a worthwhile investment.