In reading your previous posting, I understand that you use your (2 soon to be 3) PCs for business and currently only have the objective of enabling all PCs to have internet access (presumably 1 broadband connection).
It may be useful to cover some key figures first to help your decision making process;
Generally broadband speeds across the UK is 2 Mbps. Wireless 802.11g has a theoretical capacity of 54 Mbps (40-ish is a good practically achieveable target, which can drop lower occasionally). The new (next generation) 802.11n protocol has a capacity of 108 Mbps as it uses 2 802.11g channels in essence.
Wired networks are more reliable as they are not subject to radio wave interference (cordless DECT phones, microwave ovens, etc, on the same frequency band used by wireless networking devices in the UK).
They generally have 100 Mbps capacity, but can get up to 1,000 Mbps (1 Gbps) with specific cables and routers.
So if its only for broadband internet access, you can see that standard 802.11g's real-life capacity of 30-40 (best) is plenty.
Once you have your PCs networked together, you will inevitably want to do things just within your own network of 2-3 PCs. Such as being able to access files on any other PC, from any PC, as long as they are all switched on. Or to be able to print to just one printer connected to one PC which is switched on.
That will require more network capacity.
If you are patient, 802.11g will not be an issue.
If you have a customer on the phone and need fast and reliable access, its quite a different matter! :-)
I am a wireless newbie (but not a technical one) and have recently achieved 108 Mbps wireless 2-way connectivity ~ lets just say 100 Mbps as a conservative figure.
This is driven predominantly by social and pleasure objectives (streaming video) as I only use the network to access other PCs very occasionally for business (business hub is dedicated). However, I have managed to consolidate back-up methods and thereby software and hardware costs, as well as reduced complexity to manage the lot.
If you decide that 802.11g's 40 Mbps capacity is fine for your needs, you will halve the costs compared to 802.11n
(called pre-N as the new protocol has not been officially accepted and published by the IEEE, but the benefits are such that manufacturers have already sold "proprietary" products for over 1 year now, and doing good business by it).
Whichever you decide, be aware that radio transmission and reception has its limitations. So look for kit which helps that process. Specifically for PCI cards, look for those which enable you to buy and attach a separate external aerial. Some come with external aerials by design.
For PCI cards which have embedded aerials, they have a tough job being stuck low down in a PC's case and usually stuffed amongst a whole load of wires and the back of a desk. What chance has it got of receiving and transmitting good strong radio signals down there?
The positioning of your wireless router in relation to your other wireless PCs is critical ~ I have found that moving just 1 foot either ways made a huge difference in reliability and speed. And proximity to devices that generate radio waves on the same microwave frequence band.
More important then speed, given that you use it for business, is security. I would strongly recommend only short-listing kit which has the WPA rather then WEP encryption. This actually encrypts all the data you send/receive and can only be decrypted with the right key or password.
You have provided links to vendors web sites, one of which does not sell the Netgear product you mention. Try to review what your needs are and compile a short-list of products and post back for comments (I would recommend the Networking Forum for that purpose again).
Of course, individuals are unlikely to offer specific recommendations across the range of your short-list products, but collectively we should be able to.
I hope that has been of some help?