How much performance can I get from my macbook?

Question

It's older then 2,5 years but still quite good for my needs. It has a 2.16 GHz Core 2 Duo and I never use all the CPU, it has 2GB 667MHz DDR2 SDRAM and I use it all. I am not using all the 120 GB of 5400 rpm HDD but I use it often and I feel how much it is slow. Intel GMA950 is slow also, but it seems to be enough for me and is able to manage my external LCD at 1920x1200 resolution.
So I am thinking about two possible ways to have more performance:
1. get a new macbook pro of 13" with 4GB RAM, newer disk (may be faster);
2. upgrade my RAM, my Disk and may be my OS.
I know that I can use only 3.3 GB of RAM if I place 2 x 2GB 667MHz so-dimms: one more GB free could make difference for me.
About the disk, I know that my SATA is limited to 1.5 Gigabits but, using AJA System Test, I see that my internal drive is able to read and write about 29 MB/s, that seems to be even slower of my external 7200 drive that is using a Firewire 400 connection (39 MB/s).
It seems to me that newer HDDs on market, eg. Seagate Momentus.4 5400 rpm, are able to give much better transfer rate. My SATA should be able to manage transfer rates till 180MB/s so SATA II HDD should not suffer of it. Is it right?
Finally I could upgrade to Snow Leopard that should be a little bit faster then Leopard and with a completely new better finder.
So my questions are:
1. current 5400 HDD, like seagate Momentus.4, are really double or triple faster then my 2 years old hitachi? Even on my SATA controller?
2. 667 MHz RAM compared to the new 1066MHz could be a bottleneck even at 3.3 GB?
3. if I buy a new macbook pro, 2.53 GHz, 4GB RAM, 250GB HDD, how much performance difference will I notice between this new machine and mine with upgraded RAM, HDD & Os?
It's a difference of about 1.280$ (1.499$ - 220$), so I would be really pleased to listen what you think and know about this kind of upgrade.
Thanks a lot in advance.
Fabio.

Answer 1

Ok, I'll chime in with an opinion at least.
Wait on the new book. Do a $90 ram/$29 OS upgrade and give up on spending money on a HDD.
Ive been looking at upgrades to speed up my laptop till I can afford a new one and have decided to wait 12months till SSD prices drop to $1.75-$2.50/GB. I think I will windup with a faster computer than anything that will come out for another 12 more months. I love getting the latest and greatest, but since I wont be able to afford a whole new computer next year I will be happy with a much faster book.
I am using 65% of my upgraded ram(4/3.3whatever), never all of my cpu and only 35% of my drive space. Also happy with my external LCD monitor.
If this http://www.amazon.com/Intel-160GB-Mainstream-Retail-SSDSA2MH160G2R5/dp/B002IJA1E Q/ref=sr12?ie=UTF8&s=electronics&qid=1262409156&sr=8-2 hits $360 it will be a no brainer for me. The 'new computer' option will be right out the window.
Marco