By and large, the CPUs in most modern laptops are more than sufficient for any game... It's the GPU and the Memory that make the most difference nowadays and, depending upon how your machine is setup, the CPU configuration (ie Dual Core will perform significantly better if you have stuff running in the background, such as anti-virus software).
I have yet to hear a single comment on the 9300 boards claiming that a CPU upgrade made any significant improvement in performance of a game (or indeed, almost anything else).
This makes sense since the CPU is powering away at stuff until it is done and then goes to sleep waiting for the slow part of the system (the disk and, even slower, the human) to respond. If it takes a fast CPU a quarter of a second to do something, a slower CPU taking a thid of a second is still fast enough to qualify as 'instant'. Of course, if you are running something that takes 10 hours to process, you will care about the extra 30% performance, but this is not going to be a playable game !
In practice, even the GPU has limited impact on performance... going from a 6800Go to a 7800GTX will perhaps double the performance, but all of the games I know of are functional on the 6800Go... the 7800GTX is used to improve the quality of the image more than to improve gameplay, I gather. Still, a 100% improvement has more potential than the 30% going from a 1.6GHz CPU to a 2.13GHz one, especially since the 1.6 has the potential to multi-task much more efficiently...
Also, although games are rarely written specifically for dual core systems, I would expect them to sometimes spawn child processes which the dual core system should be able to optimize. This is especially true of games that are designed for multi-player use, but which are being used by a single player against computer opponents. I would expect the game machine to be one process sending and receiving messages from a process per 'player'.
In my opinion (backed by no personal experience at all), I would go with the E1705. It should currently perform around as well as the 9300 and, in the next year or two, should perform better.
Then again, I wouldn't buy an E1705 for another 3-6 months at least, since I don't trust Rev 1.00a of anything. And then, the 64 bit version will be released, so I'd then wait another 3-6 months... Keep the 9300 for a year and save your money until March 2007.