canon 50mm Primes. 1.8 or 1.4?

[witness of a past]

Hi everybody,j
I'm new to this forum, and would be very greatfull for some advice.
I am on a very steep learning curve
I'm shortly going to be celebrating my birthday, so may have bit of gift money to indulge my-hobby with.
I have Canon a 50D and a Tamron18-250 F3.5-6.3. This is my only lens, and is on my camera all the time. I am reasonably happy with it, however I have been thinking, just thinking, about investing in something a little sharper.
( My wife thinks I'm mad)
I was initially looking at the Canon 50mm 1.8. I have been told it is a very good performer despite it's plasticy build and low price. 

1st question, Would your suggest that in the long run I would be better to get the 50mm 1.4, as I've heard some people say they eventually up-grade to the better spec 1.4 version anyway.

2nd Question, Would you suggest a different permanent lens as an improvement on my tamron 18-250?

Sadly!, I don't have limitless budget to play with so that has to be a factor.
Greatfulll for your advice.

[Bob Atkins]

It depends a bit on how much you intend to use it. The optics of the EF 50/1.8 II are pretty good, but the construction is a little "plastic" and the focus is a little slow and noisy, If you don't use the lens a lot, it's fine. The EF 50/1.4 USM is a little better optically at wide apertures (but not that much better), it's 2/3 stop faster, better built, quiter and faster focusing. If you think you'll be using it a lot the 1.4 version might be a better buy.

I'm not sure there is any low cost option that will be better than your 18-250 and cover the same range. If you are happy with it, stick with it. The new Tamron 18-270 VC (vibration control) lens might be a possibility. The optics are similar, but the Optical Stabilization (Vibration Control) will make it a lot easier to get sharp handheld images at longer telephoto settings.

[witness of a past]

Bob,
         Thanks very much for your advice.