Mix ad-hoc + infrastructure mode

Hi,

I want to know if I can mix ad-hoc and infrastructure mode in one network.
My setup is as follows:

Server : Wired NIC, Wireless NIC (ad-hoc), USB ADSL
Notebook : Wireless NIC (ad-hoc)
PDA : Wireless NIC(ad-hoc)
Desktop Clients : Wired NIC

My Server routes internet traffic from for and internal traffic between the
wired and wireless networks which reside
on different sub-nets. Now I plan to purchase a device which has a build-in
10/100Mb NIC (DreamBox 7020), I want
this device to have access to the network but it will far from the wired
network therefore I was considering going wireless.
My question is, can I by an Access Point and connect it directly to the
DreamBox and have my ad-hoc wireless network
function correctly or will I have to switch to infrastructure mode.

I am concerned about the quality of the signal to the Access Point and that
is why I am hesitant about switching to infrastructure mode
(I know this sounds strange and maybe my logic is failing me here).
Currently I have good wireless coverage on top floor in the house The signal
to the lower floor is spotty, however there is a spot with good signal
quality and this is where I will place the access point. However I am
concerned that not all areas on the upper floor will have a good signal to
the access point on the lower floor and there by reduce my coverage on the
upper floor in the case that I switch to infrastructure mode.

Does any of that make sense?

--
Chris Taylor
http://dotnetjunkies.com/weblog/chris.taylor